svn commit: r322989 - in head/sys: amd64/include i386/include sys
Gleb Smirnoff
glebius at FreeBSD.org
Tue Aug 29 20:33:34 UTC 2017
Thanks, Conrad!
At Netflix we've been running that for several years already. It makes
measurable difference. I'm surprised that FreeBSD has been optimized
by default for a certain short lived generation of CPUs, and everybody
was shy to just make step forward and fix that.
On Mon, Aug 28, 2017 at 10:28:41PM +0000, Conrad Meyer wrote:
C> Author: cem
C> Date: Mon Aug 28 22:28:41 2017
C> New Revision: 322989
C> URL: https://svnweb.freebsd.org/changeset/base/322989
C>
C> Log:
C> Drop CACHE_LINE_SIZE to 64 bytes on x86
C>
C> The actual cache line size has always been 64 bytes.
C>
C> The 128 number arose as an optimization for Core 2 era Intel processors. By
C> default (configurable in BIOS), these CPUs would prefetch adjacent cache
C> lines unintelligently. Newer CPUs prefetch more intelligently.
C>
C> The latest Core 2 era CPU was introduced in September 2008 (Xeon 7400
C> series, "Dunnington"). If you are still using one of these CPUs, especially
C> in a multi-socket configuration, consider locating the "adjacent cache line
C> prefetch" option in BIOS and disabling it.
C>
C> Reported by: mjg
C> Reviewed by: np
C> Discussed with: jhb
C> Sponsored by: Dell EMC Isilon
C>
C> Modified:
C> head/sys/amd64/include/param.h
C> head/sys/i386/include/param.h
C> head/sys/sys/param.h
C>
C> Modified: head/sys/amd64/include/param.h
C> ==============================================================================
C> --- head/sys/amd64/include/param.h Mon Aug 28 22:14:16 2017 (r322988)
C> +++ head/sys/amd64/include/param.h Mon Aug 28 22:28:41 2017 (r322989)
C> @@ -89,7 +89,7 @@
C> * CACHE_LINE_SIZE is the compile-time maximum cache line size for an
C> * architecture. It should be used with appropriate caution.
C> */
C> -#define CACHE_LINE_SHIFT 7
C> +#define CACHE_LINE_SHIFT 6
C> #define CACHE_LINE_SIZE (1 << CACHE_LINE_SHIFT)
C>
C> /* Size of the level 1 page table units */
C>
C> Modified: head/sys/i386/include/param.h
C> ==============================================================================
C> --- head/sys/i386/include/param.h Mon Aug 28 22:14:16 2017 (r322988)
C> +++ head/sys/i386/include/param.h Mon Aug 28 22:28:41 2017 (r322989)
C> @@ -82,7 +82,7 @@
C> * CACHE_LINE_SIZE is the compile-time maximum cache line size for an
C> * architecture. It should be used with appropriate caution.
C> */
C> -#define CACHE_LINE_SHIFT 7
C> +#define CACHE_LINE_SHIFT 6
C> #define CACHE_LINE_SIZE (1 << CACHE_LINE_SHIFT)
C>
C> #define PAGE_SHIFT 12 /* LOG2(PAGE_SIZE) */
C>
C> Modified: head/sys/sys/param.h
C> ==============================================================================
C> --- head/sys/sys/param.h Mon Aug 28 22:14:16 2017 (r322988)
C> +++ head/sys/sys/param.h Mon Aug 28 22:28:41 2017 (r322989)
C> @@ -58,7 +58,7 @@
C> * in the range 5 to 9.
C> */
C> #undef __FreeBSD_version
C> -#define __FreeBSD_version 1200042 /* Master, propagated to newvers */
C> +#define __FreeBSD_version 1200043 /* Master, propagated to newvers */
C>
C> /*
C> * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,
C>
--
Totus tuus, Glebius.
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