linux/arch/x86
Jiri Olsa ea7145477a x86: Separate out entry text section
Put x86 entry code into a separate link section: .entry.text.

Separating the entry text section seems to have performance
benefits - caused by more efficient instruction cache usage.

Running hackbench with perf stat --repeat showed that the change
compresses the icache footprint. The icache load miss rate went
down by about 15%:

 before patch:
         19417627  L1-icache-load-misses      ( +-   0.147% )

 after patch:
         16490788  L1-icache-load-misses      ( +-   0.180% )

The motivation of the patch was to fix a particular kprobes
bug that relates to the entry text section, the performance
advantage was discovered accidentally.

Whole perf output follows:

 - results for current tip tree:

  Performance counter stats for './hackbench/hackbench 10' (500 runs):

         19417627  L1-icache-load-misses      ( +-   0.147% )
       2676914223  instructions             #      0.497 IPC     ( +- 0.079% )
       5389516026  cycles                     ( +-   0.144% )

      0.206267711  seconds time elapsed   ( +-   0.138% )

 - results for current tip tree with the patch applied:

  Performance counter stats for './hackbench/hackbench 10' (500 runs):

         16490788  L1-icache-load-misses      ( +-   0.180% )
       2717734941  instructions             #      0.502 IPC     ( +- 0.079% )
       5414756975  cycles                     ( +-   0.148% )

      0.206747566  seconds time elapsed   ( +-   0.137% )

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: masami.hiramatsu.pt@hitachi.com
Cc: ananth@in.ibm.com
Cc: davem@davemloft.net
Cc: 2nddept-manager@sdl.hitachi.co.jp
LKML-Reference: <20110307181039.GB15197@jolsa.redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-03-08 17:22:11 +01:00
..
boot x86: support XZ-compressed kernel 2011-01-13 08:03:25 -08:00
configs
crypto Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2011-01-13 10:25:58 -08:00
ia32 x86: Separate out entry text section 2011-03-08 17:22:11 +01:00
include/asm Merge commit 'v2.6.38-rc8' into perf/core 2011-03-08 17:21:52 +01:00
kernel x86: Separate out entry text section 2011-03-08 17:22:11 +01:00
kvm KVM: SVM: Advance instruction pointer in dr_intercept 2011-02-22 16:01:44 +02:00
lguest LGUEST_GUEST: fix unmet direct dependencies (VIRTUALIZATION && VIRTIO) 2011-01-20 21:37:30 +10:30
lib x86: udelay: Use this_cpu_read to avoid address calculation 2011-01-04 06:08:55 +01:00
math-emu
mm x86, nx: Don't force pages RW when setting NX bits 2011-02-02 16:02:36 -08:00
oprofile Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-01-11 11:02:13 -08:00
pci Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6 2011-01-14 09:29:05 -08:00
platform x86: OLPC: have prom_early_alloc BUG rather than return NULL 2011-03-02 13:45:18 -07:00
power
tools
vdso x86, gcc-4.6: Use gcc -m options when building vdso 2010-12-13 16:08:37 -08:00
video
xen xen/setup: Route halt operations to safe_halt pvop. 2011-01-27 12:00:24 -05:00
.gitignore
Kbuild x86: Add platform directory 2010-10-27 14:30:01 +02:00
Kconfig kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT 2011-01-20 17:02:05 -08:00
Kconfig.cpu kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT 2011-01-20 17:02:05 -08:00
Kconfig.debug kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT 2011-01-20 17:02:05 -08:00
Makefile Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-10-21 13:06:00 -07:00
Makefile_32.cpu jump label: Add work around to i386 gcc asm goto bug 2010-10-29 14:45:29 -04:00