linux/arch/x86
David Vrabel 1c32cdc633 xen/x86: avoid updating TLS descriptors if they haven't changed
When switching tasks in a Xen PV guest, avoid updating the TLS
descriptors if they haven't changed.  This improves the speed of
context switches by almost 10% as much of the time the descriptors are
the same or only one is different.

The descriptors written into the GDT by Xen are modified from the
values passed in the update_descriptor hypercall so we keep shadow
copies of the three TLS descriptors to compare against.

lmbench3 test     Before  After  Improvement
--------------------------------------------
lat_ctx -s 32 24   7.19    6.52  9%
lat_pipe          12.56   11.66  7%

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2012-07-19 15:51:57 -04:00
..
boot x86, efi stub: Add .reloc section back into image 2012-06-07 09:52:33 -07:00
configs
crypto crypto: aesni-intel - fix unaligned cbc decrypt for x86-32 2012-05-31 20:53:22 +10:00
ia32 most of set_current_blocked() callers want SIGKILL/SIGSTOP removed from set 2012-06-01 12:58:51 -04:00
include/asm xen/mce: Add mcelog support for Xen platform 2012-07-19 15:51:36 -04:00
kernel x86, MCE, AMD: Adjust initcall sequence for xen 2012-07-19 15:51:37 -04:00
kvm KVM: MMU: fix huge page adapted on non-PAE host 2012-05-28 17:41:15 +03:00
lguest
lib perf/x86: Fix broken LBR fixup code 2012-06-13 15:00:28 +02:00
math-emu
mm x86/mm: Fix some kernel-doc warnings 2012-06-11 10:54:45 +02:00
net
oprofile
pci Features: 2012-05-24 16:02:08 -07:00
platform x86/uv: Fix UV2 BAU legacy mode 2012-06-08 11:48:28 +02:00
power
realmode
syscalls syscalls, x86: add __NR_kcmp syscall 2012-05-31 17:49:32 -07:00
tools x86/decoder: Fix bsr/bsf/jmpe decoding with operand-size prefix 2012-06-06 08:54:18 +02:00
um x86, um: Correct syscall table type attributes breaking gcc 4.8 2012-06-09 12:51:09 -07:00
vdso
video
xen xen/x86: avoid updating TLS descriptors if they haven't changed 2012-07-19 15:51:57 -04:00
.gitignore
Kbuild
Kconfig x86, efi: Add EFI boot stub documentation 2012-06-01 09:11:41 -07:00
Kconfig.cpu
Kconfig.debug
Makefile
Makefile_32.cpu
Makefile.um