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. _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
