lkml.org 
[lkml]   [2011]   [Mar]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:perf/core] x86: Separate out entry text section
Commit-ID:  ea7145477a461e09d8d194cac4b996dc4f449107
Gitweb: http://git.kernel.org/tip/ea7145477a461e09d8d194cac4b996dc4f449107
Author: Jiri Olsa <jolsa@redhat.com>
AuthorDate: Mon, 7 Mar 2011 19:10:39 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 8 Mar 2011 17:22:11 +0100

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>
---
arch/x86/ia32/ia32entry.S | 2 ++
arch/x86/kernel/entry_32.S | 6 ++++--
arch/x86/kernel/entry_64.S | 6 ++++--
arch/x86/kernel/vmlinux.lds.S | 1 +
include/asm-generic/sections.h | 1 +
include/asm-generic/vmlinux.lds.h | 6 ++++++
6 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 518bb99..f729b2e 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -25,6 +25,8 @@
#define sysretl_audit ia32_ret_from_sys_call
#endif

+ .section .entry.text, "ax"
+
#define IA32_NR_syscalls ((ia32_syscall_end - ia32_sys_call_table)/8)

.macro IA32_ARG_FIXUP noebp=0
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index c8b4efa..f5accf8 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 aed1ffb..0a0ed79 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 bf47007..6d4341d 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)
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index b3bfabc..c1a1216 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -11,6 +11,7 @@ extern char _sinittext[], _einittext[];
extern char _end[];
extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[];
extern char __kprobes_text_start[], __kprobes_text_end[];
+extern char __entry_text_start[], __entry_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __start_rodata[], __end_rodata[];

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index fe77e33..906c3ce 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -424,6 +424,12 @@
*(.kprobes.text) \
VMLINUX_SYMBOL(__kprobes_text_end) = .;

+#define ENTRY_TEXT \
+ ALIGN_FUNCTION(); \
+ VMLINUX_SYMBOL(__entry_text_start) = .; \
+ *(.entry.text) \
+ VMLINUX_SYMBOL(__entry_text_end) = .;
+
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
#define IRQENTRY_TEXT \
ALIGN_FUNCTION(); \

\
 
 \ /
  Last update: 2011-03-08 21:19    [W:0.063 / U:5.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site