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linux/include/asm-generic/cmpxchg-local.h

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 14:07:57 +00:00
/* SPDX-License-Identifier: GPL-2.0 */
Add cmpxchg_local to asm-generic for per cpu atomic operations Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-07 08:16:07 +00:00
#ifndef __ASM_GENERIC_CMPXCHG_LOCAL_H
#define __ASM_GENERIC_CMPXCHG_LOCAL_H
#include <linux/types.h>
Fix IRQ flag handling naming Fix the IRQ flag handling naming. In linux/irqflags.h under one configuration, it maps: local_irq_enable() -> raw_local_irq_enable() local_irq_disable() -> raw_local_irq_disable() local_irq_save() -> raw_local_irq_save() ... and under the other configuration, it maps: raw_local_irq_enable() -> local_irq_enable() raw_local_irq_disable() -> local_irq_disable() raw_local_irq_save() -> local_irq_save() ... This is quite confusing. There should be one set of names expected of the arch, and this should be wrapped to give another set of names that are expected by users of this facility. Change this to have the arch provide: flags = arch_local_save_flags() flags = arch_local_irq_save() arch_local_irq_restore(flags) arch_local_irq_disable() arch_local_irq_enable() arch_irqs_disabled_flags(flags) arch_irqs_disabled() arch_safe_halt() Then linux/irqflags.h wraps these to provide: raw_local_save_flags(flags) raw_local_irq_save(flags) raw_local_irq_restore(flags) raw_local_irq_disable() raw_local_irq_enable() raw_irqs_disabled_flags(flags) raw_irqs_disabled() raw_safe_halt() with type checking on the flags 'arguments', and then wraps those to provide: local_save_flags(flags) local_irq_save(flags) local_irq_restore(flags) local_irq_disable() local_irq_enable() irqs_disabled_flags(flags) irqs_disabled() safe_halt() with tracing included if enabled. The arch functions can now all be inline functions rather than some of them having to be macros. Signed-off-by: David Howells <dhowells@redhat.com> [X86, FRV, MN10300] Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> [Tile] Signed-off-by: Michal Simek <monstr@monstr.eu> [Microblaze] Tested-by: Catalin Marinas <catalin.marinas@arm.com> [ARM] Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> [AVR] Acked-by: Tony Luck <tony.luck@intel.com> [IA-64] Acked-by: Hirokazu Takata <takata@linux-m32r.org> [M32R] Acked-by: Greg Ungerer <gerg@uclinux.org> [M68K/M68KNOMMU] Acked-by: Ralf Baechle <ralf@linux-mips.org> [MIPS] Acked-by: Kyle McMartin <kyle@mcmartin.ca> [PA-RISC] Acked-by: Paul Mackerras <paulus@samba.org> [PowerPC] Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> [S390] Acked-by: Chen Liqin <liqin.chen@sunplusct.com> [Score] Acked-by: Matt Fleming <matt@console-pimps.org> [SH] Acked-by: David S. Miller <davem@davemloft.net> [Sparc] Acked-by: Chris Zankel <chris@zankel.net> [Xtensa] Reviewed-by: Richard Henderson <rth@twiddle.net> [Alpha] Reviewed-by: Yoshinori Sato <ysato@users.sourceforge.jp> [H8300] Cc: starvik@axis.com [CRIS] Cc: jesper.nilsson@axis.com [CRIS] Cc: linux-cris-kernel@axis.com
2010-10-07 13:08:55 +00:00
#include <linux/irqflags.h>
Add cmpxchg_local to asm-generic for per cpu atomic operations Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-07 08:16:07 +00:00
LLVMLinux: Remove warning about returning an uninitialized variable Fix uninitialized return code in default case in cmpxchg-local.h This patch fixes the code to prevent an uninitialized return value that is detected when compiling with clang. The bug produces numerous warnings when compiling the Linux kernel with clang. Signed-off-by: Behan Webster <behanw@converseincode.com> Signed-off-by: Mark Charlebois <charlebm@gmail.com> Acked-by: David Howells <dhowells@redhat.com> Acked-by: Arnd Bergmann <arnd@arndb.de>
2012-11-20 20:19:50 +00:00
extern unsigned long wrong_size_cmpxchg(volatile void *ptr)
__noreturn;
Add cmpxchg_local to asm-generic for per cpu atomic operations Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-07 08:16:07 +00:00
/*
* Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned
* long parameter, supporting various types of architectures.
*/
static inline unsigned long __cmpxchg_local_generic(volatile void *ptr,
unsigned long old, unsigned long new, int size)
{
unsigned long flags, prev;
/*
* Sanity checking, compile-time.
*/
if (size == 8 && sizeof(unsigned long) != 8)
wrong_size_cmpxchg(ptr);
generic: Use raw local irq variant for generic cmpxchg The interrupt disabled region is extremly tiny and therefor not latency relevant. Avoid cluttering the traces with those pointless entries. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-03 13:29:30 +00:00
raw_local_irq_save(flags);
Add cmpxchg_local to asm-generic for per cpu atomic operations Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-07 08:16:07 +00:00
switch (size) {
case 1: prev = *(u8 *)ptr;
if (prev == old)
*(u8 *)ptr = (u8)new;
break;
case 2: prev = *(u16 *)ptr;
if (prev == old)
*(u16 *)ptr = (u16)new;
break;
case 4: prev = *(u32 *)ptr;
if (prev == old)
*(u32 *)ptr = (u32)new;
break;
case 8: prev = *(u64 *)ptr;
if (prev == old)
*(u64 *)ptr = (u64)new;
break;
default:
wrong_size_cmpxchg(ptr);
}
generic: Use raw local irq variant for generic cmpxchg The interrupt disabled region is extremly tiny and therefor not latency relevant. Avoid cluttering the traces with those pointless entries. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-03 13:29:30 +00:00
raw_local_irq_restore(flags);
Add cmpxchg_local to asm-generic for per cpu atomic operations Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-07 08:16:07 +00:00
return prev;
}
/*
* Generic version of __cmpxchg64_local. Takes an u64 parameter.
*/
static inline u64 __cmpxchg64_local_generic(volatile void *ptr,
u64 old, u64 new)
{
u64 prev;
unsigned long flags;
generic: Use raw local irq variant for generic cmpxchg The interrupt disabled region is extremly tiny and therefor not latency relevant. Avoid cluttering the traces with those pointless entries. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-03 13:29:30 +00:00
raw_local_irq_save(flags);
Add cmpxchg_local to asm-generic for per cpu atomic operations Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-07 08:16:07 +00:00
prev = *(u64 *)ptr;
if (prev == old)
*(u64 *)ptr = new;
generic: Use raw local irq variant for generic cmpxchg The interrupt disabled region is extremly tiny and therefor not latency relevant. Avoid cluttering the traces with those pointless entries. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-07-03 13:29:30 +00:00
raw_local_irq_restore(flags);
Add cmpxchg_local to asm-generic for per cpu atomic operations Emulates the cmpxchg_local by disabling interrupts around variable modification. This is not reentrant wrt NMIs and MCEs. It is only protected against normal interrupts, but this is enough for architectures without such interrupt sources or if used in a context where the data is not shared with such handlers. It can be used as a fallback for architectures lacking a real cmpxchg instruction. For architectures that have a real cmpxchg but does not have NMIs or MCE, testing which of the generic vs architecture specific cmpxchg is the fastest should be done. asm-generic/cmpxchg.h defines a cmpxchg that uses cmpxchg_local. It is meant to be used as a cmpxchg fallback for architectures that do not support SMP. * Patch series comments Using cmpxchg_local shows a performance improvements of the fast path goes from a 66% speedup on a Pentium 4 to a 14% speedup on AMD64. In detail: Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a Pentium4, 3GHz, Hyperthread. SLUB Performance testing ======================== 1. Kmalloc: Repeatedly allocate then free test * slub HEAD, test 1 kmalloc(8) = 201 cycles kfree = 351 cycles kmalloc(16) = 198 cycles kfree = 359 cycles kmalloc(32) = 200 cycles kfree = 381 cycles kmalloc(64) = 224 cycles kfree = 394 cycles kmalloc(128) = 285 cycles kfree = 424 cycles kmalloc(256) = 411 cycles kfree = 546 cycles kmalloc(512) = 480 cycles kfree = 619 cycles kmalloc(1024) = 623 cycles kfree = 750 cycles kmalloc(2048) = 686 cycles kfree = 811 cycles kmalloc(4096) = 482 cycles kfree = 538 cycles kmalloc(8192) = 680 cycles kfree = 734 cycles kmalloc(16384) = 713 cycles kfree = 843 cycles * Slub HEAD, test 2 kmalloc(8) = 190 cycles kfree = 351 cycles kmalloc(16) = 195 cycles kfree = 360 cycles kmalloc(32) = 201 cycles kfree = 370 cycles kmalloc(64) = 245 cycles kfree = 389 cycles kmalloc(128) = 283 cycles kfree = 413 cycles kmalloc(256) = 409 cycles kfree = 547 cycles kmalloc(512) = 476 cycles kfree = 616 cycles kmalloc(1024) = 628 cycles kfree = 753 cycles kmalloc(2048) = 684 cycles kfree = 811 cycles kmalloc(4096) = 480 cycles kfree = 539 cycles kmalloc(8192) = 661 cycles kfree = 746 cycles kmalloc(16384) = 741 cycles kfree = 856 cycles * cmpxchg_local Slub test kmalloc(8) = 83 cycles kfree = 363 cycles kmalloc(16) = 85 cycles kfree = 372 cycles kmalloc(32) = 92 cycles kfree = 377 cycles kmalloc(64) = 115 cycles kfree = 397 cycles kmalloc(128) = 179 cycles kfree = 438 cycles kmalloc(256) = 314 cycles kfree = 564 cycles kmalloc(512) = 398 cycles kfree = 615 cycles kmalloc(1024) = 573 cycles kfree = 745 cycles kmalloc(2048) = 629 cycles kfree = 816 cycles kmalloc(4096) = 473 cycles kfree = 548 cycles kmalloc(8192) = 659 cycles kfree = 745 cycles kmalloc(16384) = 724 cycles kfree = 843 cycles 2. Kmalloc: alloc/free test * slub HEAD, test 1 kmalloc(8)/kfree = 322 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 325 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 678 cycles kmalloc(8192)/kfree = 1013 cycles kmalloc(16384)/kfree = 1157 cycles * Slub HEAD, test 2 kmalloc(8)/kfree = 323 cycles kmalloc(16)/kfree = 318 cycles kmalloc(32)/kfree = 318 cycles kmalloc(64)/kfree = 318 cycles kmalloc(128)/kfree = 318 cycles kmalloc(256)/kfree = 328 cycles kmalloc(512)/kfree = 328 cycles kmalloc(1024)/kfree = 328 cycles kmalloc(2048)/kfree = 328 cycles kmalloc(4096)/kfree = 648 cycles kmalloc(8192)/kfree = 1009 cycles kmalloc(16384)/kfree = 1105 cycles * cmpxchg_local Slub test kmalloc(8)/kfree = 112 cycles kmalloc(16)/kfree = 103 cycles kmalloc(32)/kfree = 103 cycles kmalloc(64)/kfree = 103 cycles kmalloc(128)/kfree = 112 cycles kmalloc(256)/kfree = 111 cycles kmalloc(512)/kfree = 111 cycles kmalloc(1024)/kfree = 111 cycles kmalloc(2048)/kfree = 121 cycles kmalloc(4096)/kfree = 650 cycles kmalloc(8192)/kfree = 1042 cycles kmalloc(16384)/kfree = 1149 cycles Tested-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Measurements on a AMD64 2.0 GHz dual-core In this test, we seem to remove 10 cycles from the kmalloc fast path. On small allocations, it gives a 14% performance increase. kfree fast path also seems to have a 10 cycles improvement. 1. Kmalloc: Repeatedly allocate then free test * cmpxchg_local slub kmalloc(8) = 63 cycles kfree = 126 cycles kmalloc(16) = 66 cycles kfree = 129 cycles kmalloc(32) = 76 cycles kfree = 138 cycles kmalloc(64) = 100 cycles kfree = 288 cycles kmalloc(128) = 128 cycles kfree = 309 cycles kmalloc(256) = 170 cycles kfree = 315 cycles kmalloc(512) = 221 cycles kfree = 357 cycles kmalloc(1024) = 324 cycles kfree = 393 cycles kmalloc(2048) = 354 cycles kfree = 440 cycles kmalloc(4096) = 394 cycles kfree = 330 cycles kmalloc(8192) = 523 cycles kfree = 481 cycles kmalloc(16384) = 643 cycles kfree = 649 cycles * Base kmalloc(8) = 74 cycles kfree = 113 cycles kmalloc(16) = 76 cycles kfree = 116 cycles kmalloc(32) = 85 cycles kfree = 133 cycles kmalloc(64) = 111 cycles kfree = 279 cycles kmalloc(128) = 138 cycles kfree = 294 cycles kmalloc(256) = 181 cycles kfree = 304 cycles kmalloc(512) = 237 cycles kfree = 327 cycles kmalloc(1024) = 340 cycles kfree = 379 cycles kmalloc(2048) = 378 cycles kfree = 433 cycles kmalloc(4096) = 399 cycles kfree = 329 cycles kmalloc(8192) = 528 cycles kfree = 624 cycles kmalloc(16384) = 651 cycles kfree = 737 cycles 2. Kmalloc: alloc/free test * cmpxchg_local slub kmalloc(8)/kfree = 96 cycles kmalloc(16)/kfree = 97 cycles kmalloc(32)/kfree = 97 cycles kmalloc(64)/kfree = 97 cycles kmalloc(128)/kfree = 97 cycles kmalloc(256)/kfree = 105 cycles kmalloc(512)/kfree = 108 cycles kmalloc(1024)/kfree = 105 cycles kmalloc(2048)/kfree = 107 cycles kmalloc(4096)/kfree = 390 cycles kmalloc(8192)/kfree = 626 cycles kmalloc(16384)/kfree = 662 cycles * Base kmalloc(8)/kfree = 116 cycles kmalloc(16)/kfree = 116 cycles kmalloc(32)/kfree = 116 cycles kmalloc(64)/kfree = 116 cycles kmalloc(128)/kfree = 116 cycles kmalloc(256)/kfree = 126 cycles kmalloc(512)/kfree = 126 cycles kmalloc(1024)/kfree = 126 cycles kmalloc(2048)/kfree = 126 cycles kmalloc(4096)/kfree = 384 cycles kmalloc(8192)/kfree = 749 cycles kmalloc(16384)/kfree = 786 cycles Tested-by: Christoph Lameter <clameter@sgi.com> I can confirm Mathieus' measurement now: Athlon64: regular NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 79 cycles kfree -> 92 cycles 10000 times kmalloc(16) -> 79 cycles kfree -> 93 cycles 10000 times kmalloc(32) -> 88 cycles kfree -> 95 cycles 10000 times kmalloc(64) -> 124 cycles kfree -> 132 cycles 10000 times kmalloc(128) -> 157 cycles kfree -> 247 cycles 10000 times kmalloc(256) -> 200 cycles kfree -> 257 cycles 10000 times kmalloc(512) -> 250 cycles kfree -> 277 cycles 10000 times kmalloc(1024) -> 337 cycles kfree -> 314 cycles 10000 times kmalloc(2048) -> 365 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 352 cycles kfree -> 240 cycles 10000 times kmalloc(8192) -> 456 cycles kfree -> 340 cycles 10000 times kmalloc(16384) -> 646 cycles kfree -> 471 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 124 cycles 10000 times kmalloc(16)/kfree -> 124 cycles 10000 times kmalloc(32)/kfree -> 124 cycles 10000 times kmalloc(64)/kfree -> 124 cycles 10000 times kmalloc(128)/kfree -> 124 cycles 10000 times kmalloc(256)/kfree -> 132 cycles 10000 times kmalloc(512)/kfree -> 132 cycles 10000 times kmalloc(1024)/kfree -> 132 cycles 10000 times kmalloc(2048)/kfree -> 132 cycles 10000 times kmalloc(4096)/kfree -> 319 cycles 10000 times kmalloc(8192)/kfree -> 486 cycles 10000 times kmalloc(16384)/kfree -> 539 cycles cmpxchg_local NUMA/discontig 1. Kmalloc: Repeatedly allocate then free test 10000 times kmalloc(8) -> 55 cycles kfree -> 90 cycles 10000 times kmalloc(16) -> 55 cycles kfree -> 92 cycles 10000 times kmalloc(32) -> 70 cycles kfree -> 91 cycles 10000 times kmalloc(64) -> 100 cycles kfree -> 141 cycles 10000 times kmalloc(128) -> 128 cycles kfree -> 233 cycles 10000 times kmalloc(256) -> 172 cycles kfree -> 251 cycles 10000 times kmalloc(512) -> 225 cycles kfree -> 275 cycles 10000 times kmalloc(1024) -> 325 cycles kfree -> 311 cycles 10000 times kmalloc(2048) -> 346 cycles kfree -> 330 cycles 10000 times kmalloc(4096) -> 351 cycles kfree -> 238 cycles 10000 times kmalloc(8192) -> 450 cycles kfree -> 342 cycles 10000 times kmalloc(16384) -> 630 cycles kfree -> 546 cycles 2. Kmalloc: alloc/free test 10000 times kmalloc(8)/kfree -> 81 cycles 10000 times kmalloc(16)/kfree -> 81 cycles 10000 times kmalloc(32)/kfree -> 81 cycles 10000 times kmalloc(64)/kfree -> 81 cycles 10000 times kmalloc(128)/kfree -> 81 cycles 10000 times kmalloc(256)/kfree -> 91 cycles 10000 times kmalloc(512)/kfree -> 90 cycles 10000 times kmalloc(1024)/kfree -> 91 cycles 10000 times kmalloc(2048)/kfree -> 90 cycles 10000 times kmalloc(4096)/kfree -> 318 cycles 10000 times kmalloc(8192)/kfree -> 483 cycles 10000 times kmalloc(16384)/kfree -> 536 cycles Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-07 08:16:07 +00:00
return prev;
}
#endif
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