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813312110b
linux/arch/powerpc
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Sukadev Bhattiprolu 813312110b powerpc/perf: Use pmc_overflow() to detect rolled back events 
For certain speculative events on Power7, 'perf stat' reports far higher
event count than 'perf record' for the same event.

As described in following commit, a performance monitor exception is raised
even when the the performance events are rolled back.

        commit 0837e3242c
        Author: Anton Blanchard <anton@samba.org>
        Date:   Wed Mar 9 14:38:42 2011 +1100

perf_event_interrupt() records an event only when an overflow occurs. But
this check for overflow is a simple 'if (val < 0)'.

Because the events are rolled back, this check for overflow fails and the
event is not recorded. perf_event_interrupt() later uses pmc_overflow() to
detect the overflow and resets the counters and the events are lost completely.

To properly detect the overflow of rolled back events, use pmc_overflow()
even when recording events.

To reproduce:
        $ cat strcpy.c
        #include <stdio.h>
        #include <string.h>
        main()
        {
                char buf[256];

                alarm(5);
                while(1)
                        strcpy(buf, "string1");
        }

        $ perf record -e r20014 ./strcpy
        $ perf report -n > report.1
        $ perf stat -e r20014 > report.2
        # Compare report.1 and report.2

Reported-by: Maynard Johnson <mpjohn@us.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2012-08-24 20:26:10 +10:00
..
boot powerpc/p4080ds: dts - add usb controller version info and port0 2012-08-10 07:47:02 -05:00
configs powerpc/fsl: fix "Failed to mount /dev: No such device" errors 2012-08-23 10:46:20 -05:00
include/asm powerpc: Remove unnecessary ifdefs 2012-08-24 20:26:06 +10:00
kernel powerpc: Fix personality handling in ppc64_personality() 2012-08-24 20:26:07 +10:00
kvm powerpc/kvm/book3s_32: Fix MTMSR_EERI macro 2012-07-31 15:21:20 +10:00
lib powerpc: Fix VMX in interrupt check in POWER7 copy loops 2012-08-24 20:26:09 +10:00
math-emu
mm powerpc: Use CURRENT_THREAD_INFO instead of open coded assembly 2012-07-11 14:18:22 +10:00
net powerpc: Start using ___PPC_RA/B/S/T where necessary 2012-07-10 19:18:25 +10:00
oprofile Disintegrate asm/system.h for PowerPC 2012-03-28 18:30:02 +01:00
perf powerpc/perf: Use pmc_overflow() to detect rolled back events 2012-08-24 20:26:10 +10:00
platforms Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-08-01 10:26:23 -07:00
sysdev powerpc/mpic_msgr: Add missing includes 2012-08-24 20:26:04 +10:00
xmon powerpc: Fixup whitespace in xmon 2012-08-24 20:26:03 +10:00
Kconfig ipc: use Kconfig options for __ARCH_WANT_[COMPAT_]IPC_PARSE_VERSION 2012-07-30 17:25:21 -07:00
Kconfig.debug powerpc: IOMMU fault injection 2012-07-10 19:18:59 +10:00
Makefile crypto: nx - move nx build to driver/crypto Makefile 2012-06-27 14:42:00 +08:00
relocs_check.pl