Date: Fri, 11 May 2018 07:04:58 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r333484 - head/sys/vm Message-ID: <201805110704.w4B74wA2037309@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: mjg Date: Fri May 11 07:04:57 2018 New Revision: 333484 URL: https://svnweb.freebsd.org/changeset/base/333484 Log: uma: increase alignment to 128 bytes on amd64 Current UMA internals are not suited for efficient operation in multi-socket environments. In particular there is very common use of MAXCPU arrays and other fields which are not always properly aligned and are not local for target threads (apart from the first node of course). Turns out the existing UMA_ALIGN macro can be used to mostly work around the problem until the code get fixed. The current setting of 64 bytes runs into trouble when adjacent cache line prefetcher gets to work. An example 128-way benchmark doing a lot of malloc/frees has the following instruction samples: before: kernel`lf_advlockasync+0x43b 32940 kernel`malloc+0xe5 42380 kernel`bzero+0x19 47798 kernel`spinlock_exit+0x26 60423 kernel`0xffffffff80 78238 0x0 136947 kernel`uma_zfree_arg+0x46 159594 kernel`uma_zalloc_arg+0x672 180556 kernel`uma_zfree_arg+0x2a 459923 kernel`uma_zalloc_arg+0x5ec 489910 after: kernel`bzero+0xd 46115 kernel`lf_advlockasync+0x25f 46134 kernel`lf_advlockasync+0x38a 49078 kernel`fget_unlocked+0xd1 49942 kernel`lf_advlockasync+0x43b 55392 kernel`copyin+0x4a 56963 kernel`bzero+0x19 81983 kernel`spinlock_exit+0x26 91889 kernel`0xffffffff80 136357 0x0 239424 See the review for more details. Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D15346 Modified: head/sys/vm/uma_int.h Modified: head/sys/vm/uma_int.h ============================================================================== --- head/sys/vm/uma_int.h Fri May 11 06:59:54 2018 (r333483) +++ head/sys/vm/uma_int.h Fri May 11 07:04:57 2018 (r333484) @@ -177,7 +177,7 @@ struct uma_hash { * align field or structure to cache line */ #if defined(__amd64__) -#define UMA_ALIGN __aligned(CACHE_LINE_SIZE) +#define UMA_ALIGN __aligned(128) #else #define UMA_ALIGN #endif
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201805110704.w4B74wA2037309>