Messages in this thread Patch in this message | | | Date | Fri, 1 Jul 2005 22:57:00 -0400 | From | Chuck Ebbert <> | Subject | Re: [RFC] exit_thread() speedups in x86 process.c |
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On Wed, 22 Jun 2005 at 04:41:47 -0400, cutaway wrote:
> The compilers got tweaked to be able to emit > function code to different text sections and a massive system wide code > triage was undertaken based on "common usage scenario" profiling run data > from the perf analysis group.
Linux scheduler code is in its own text section already, but that might be for profiling the code instead of for performance. (Look for "__sched" in the source code.)
The gains may not be as much as you think since on X86 and at least some other archs the entire kernel is in one large page. Still, it's got to make some kind of sense to put infrequently-used code in its own section just to reduce cache pollution.
I came up with this but only the "__slow" part really makes sense:
--- 2.6.12.1/arch/i386/kernel/vmlinux.lds.S 2004-09-03 19:55:27.000000000 -0400 +++ 2.6.12.1-ce1/arch/i386/kernel/vmlinux.lds.S 2005-06-26 01:48:23.770212000 -0400 @@ -16,9 +16,11 @@ SECTIONS /* read-only */ _text = .; /* Text and read-only data */ .text : { + *(.fast.text) *(.text) SCHED_TEXT LOCK_TEXT + *(.slow.text) *(.fixup) *(.gnu.warning) } = 0x9090 --- 2.6.12.1/arch/x86_64/kernel/vmlinux.lds.S 2005-06-24 00:50:21.180212000 -0400 +++ 2.6.12.1-ce1/arch/x86_64/kernel/vmlinux.lds.S 2005-06-26 01:50:09.100212000 -0400 @@ -15,9 +15,11 @@ SECTIONS phys_startup_64 = startup_64 - LOAD_OFFSET; _text = .; /* Text and read-only data */ .text : { + *(.fast.text) *(.text) SCHED_TEXT LOCK_TEXT + *(.slow.text) *(.fixup) *(.gnu.warning) } = 0x9090 --- 2.6.12.1/include/linux/init.h 2005-01-04 21:48:02.000000000 -0500 +++ 2.6.12.1-ce1/include/linux/init.h 2005-06-26 01:59:29.580212000 -0400 @@ -46,6 +46,17 @@ #define __exitdata __attribute__ ((__section__(".exit.data"))) #define __exit_call __attribute_used__ __attribute__ ((__section__ (".exitcall.exit"))) +/* + * Probably belongs in some other header (compiler.h?) + */ +#ifdef CONFIG_X86 +#define __fast __attribute__ ((__section__(".fast.text"))) +#define __slow __attribute__ ((__section__(".slow.text"))) +#else +#define __fast +#define __slow +#endif + #ifdef MODULE #define __exit __attribute__ ((__section__(".exit.text"))) #else -- Chuck - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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