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| author | Jiri Olsa <jolsa@redhat.com> | 2011-03-07 19:10:39 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-03-08 17:22:11 +0100 |
| commit | ea7145477a461e09d8d194cac4b996dc4f449107 (patch) | |
| tree | aa45594b6303b854f5fa85f82ba5dca01e0aa8ac /arch/x86/kernel | |
| parent | Merge commit 'v2.6.38-rc8' into perf/core (diff) | |
| download | linux-ea7145477a461e09d8d194cac4b996dc4f449107.tar.xz linux-ea7145477a461e09d8d194cac4b996dc4f449107.zip | |
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>
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/entry_32.S | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/vmlinux.lds.S | 1 |
3 files changed, 9 insertions, 4 deletions
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index c8b4efad7ebb..f5accf8eaa78 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -65,6 +65,8 @@ #define sysexit_audit syscall_exit_work #endif + .section .entry.text, "ax" + /* * We use macros for low-level operations which need to be overridden * for paravirtualization. The following will never clobber any registers: @@ -788,7 +790,7 @@ ENDPROC(ptregs_clone) */ .section .init.rodata,"a" ENTRY(interrupt) -.text +.section .entry.text, "ax" .p2align 5 .p2align CONFIG_X86_L1_CACHE_SHIFT ENTRY(irq_entries_start) @@ -807,7 +809,7 @@ vector=FIRST_EXTERNAL_VECTOR .endif .previous .long 1b - .text + .section .entry.text, "ax" vector=vector+1 .endif .endr diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index aed1ffbeb0c9..0a0ed794edb2 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -61,6 +61,8 @@ #define __AUDIT_ARCH_LE 0x40000000 .code64 + .section .entry.text, "ax" + #ifdef CONFIG_FUNCTION_TRACER #ifdef CONFIG_DYNAMIC_FTRACE ENTRY(mcount) @@ -744,7 +746,7 @@ END(stub_rt_sigreturn) */ .section .init.rodata,"a" ENTRY(interrupt) - .text + .section .entry.text .p2align 5 .p2align CONFIG_X86_L1_CACHE_SHIFT ENTRY(irq_entries_start) @@ -763,7 +765,7 @@ vector=FIRST_EXTERNAL_VECTOR .endif .previous .quad 1b - .text + .section .entry.text vector=vector+1 .endif .endr diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index bf4700755184..6d4341d5c52a 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -105,6 +105,7 @@ SECTIONS SCHED_TEXT LOCK_TEXT KPROBES_TEXT + ENTRY_TEXT IRQENTRY_TEXT *(.fixup) *(.gnu.warning) |