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Date: Thu, 23 Apr 2015 23:53:57 +0800 From: Daniel J Blueman <daniel@...ascale.com> To: Mel Gorman <mgorman@...e.de> Cc: Linux-MM <linux-mm@...ck.org>, Nathan Zimmer <nzimmer@....com>, Dave Hansen <dave.hansen@...el.com>, Waiman Long <waiman.long@...com>, Scott Norton <scott.norton@...com>, Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>, 'Steffen Persvold' <sp@...ascale.com> Subject: Re: [PATCH 0/13] Parallel struct page initialisation v3 On Thu, Apr 23, 2015 at 6:33 PM, Mel Gorman <mgorman@...e.de> wrote: > The big change here is an adjustment to the topology_init path that > caused > soft lockups on Waiman and Daniel Blue had reported it was an > expensive > function. > > Changelog since v2 > o Reduce overhead of topology_init > o Remove boot-time kernel parameter to enable/disable > o Enable on UMA > > Changelog since v1 > o Always initialise low zones > o Typo corrections > o Rename parallel mem init to parallel struct page init > o Rebase to 4.0 [] Splendid work! On this 256c setup, topology_init now takes 185ms. This brings the kernel boot time down to 324s [1]. It turns out that one memset is responsible for most of the time setting up the the PUDs and PMDs; adapting memset to using non-temporal writes [3] avoids generating RMW cycles, bringing boot time down to 186s [2]. If this is a possibility, I can split this patch and map other arch's memset_nocache to memset, or change the callsite as preferred; comments welcome. Thanks, Daniel [1] https://resources.numascale.com/telemetry/defermem/h8qgl-defer2.txt [2] https://resources.numascale.com/telemetry/defermem/h8qgl-defer2-nontemporal.txt -- [3] From f822139736cab8434302693c635fa146b465273c Mon Sep 17 00:00:00 2001 From: Daniel J Blueman <daniel@...ascale.com> Date: Thu, 23 Apr 2015 23:26:27 +0800 Subject: [RFC] Speedup PMD setup Using non-temporal writes prevents read-modify-write cycles, which are much slower over large topologies. Adapt the existing memset() function into a _nocache variant and use when setting up PMDs during early boot to reduce boot time. Signed-off-by: Daniel J Blueman <daniel@...ascale.com> --- arch/x86/include/asm/string_64.h | 3 ++ arch/x86/lib/memset_64.S | 90 ++++++++++++++++++++++++++++++++++++++++ mm/memblock.c | 2 +- 3 files changed, 94 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index e466119..1ef28d0 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -55,6 +55,8 @@ extern void *memcpy(void *to, const void *from, size_t len); #define __HAVE_ARCH_MEMSET void *memset(void *s, int c, size_t n); void *__memset(void *s, int c, size_t n); +void *memset_nocache(void *s, int c, size_t n); +void *__memset_nocache(void *s, int c, size_t n); #define __HAVE_ARCH_MEMMOVE void *memmove(void *dest, const void *src, size_t count); @@ -77,6 +79,7 @@ int strcmp(const char *cs, const char *ct); #define memcpy(dst, src, len) __memcpy(dst, src, len) #define memmove(dst, src, len) __memmove(dst, src, len) #define memset(s, c, n) __memset(s, c, n) +#define memset_nocache(s, c, n) __memset_nocache(s, c, n) #endif #endif /* __KERNEL__ */ diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S index 6f44935..fb46f78 100644 --- a/arch/x86/lib/memset_64.S +++ b/arch/x86/lib/memset_64.S @@ -137,6 +137,96 @@ ENTRY(__memset) ENDPROC(memset) ENDPROC(__memset) +/* + * bzero_nocache - set a memory block to zero. This function uses + * non-temporal writes in the fastpath + * + * rdi destination + * rsi value (char) + * rdx count (bytes) + * + * rax original destination + */ + +ENTRY(memset_nocache) +ENTRY(__memset_nocache) + CFI_STARTPROC + movq %rdi,%r10 + + /* expand byte value */ + movzbl %sil,%ecx + movabs $0x0101010101010101,%rax + imulq %rcx,%rax + + /* align dst */ + movl %edi,%r9d + andl $7,%r9d + jnz bad_alignment + CFI_REMEMBER_STATE +after_bad_alignment: + + movq %rdx,%rcx + shrq $6,%rcx + jz handle_tail + + .p2align 4 +loop_64: + decq %rcx + movnti %rax,(%rdi) + movnti %rax,8(%rdi) + movnti %rax,16(%rdi) + movnti %rax,24(%rdi) + movnti %rax,32(%rdi) + movnti %rax,40(%rdi) + movnti %rax,48(%rdi) + movnti %rax,56(%rdi) + leaq 64(%rdi),%rdi + jnz loop_64 + + /* Handle tail in loops; the loops should be faster than hard + to predict jump tables */ + .p2align 4 +handle_tail: + movl %edx,%ecx + andl $63&(~7),%ecx + jz handle_7 + shrl $3,%ecx + .p2align 4 +loop_8: + decl %ecx + movnti %rax,(%rdi) + leaq 8(%rdi),%rdi + jnz loop_8 + +handle_7: + andl $7,%edx + jz ende + .p2align 4 +loop_1: + decl %edx + movb %al,(%rdi) + leaq 1(%rdi),%rdi + jnz loop_1 + +ende: + movq %r10,%rax + ret + + CFI_RESTORE_STATE +bad_alignment: + cmpq $7,%rdx + jbe handle_7 + movnti %rax,(%rdi) /* unaligned store */ + movq $8,%r8 + subq %r9,%r8 + addq %r8,%rdi + subq %r8,%rdx + jmp after_bad_alignment +final: + CFI_ENDPROC +ENDPROC(memset_nocache) +ENDPROC(__memset_nocache) + /* Some CPUs support enhanced REP MOVSB/STOSB feature. * It is recommended to use this when possible. * diff --git a/mm/memblock.c b/mm/memblock.c index f3e97d8..df434d2 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -1212,7 +1212,7 @@ again: done: memblock_reserve(alloc, size); ptr = phys_to_virt(alloc); - memset(ptr, 0, size); + memset_nocache(ptr, 0, size); /* * The min_count is set to 0 so that bootmem allocated blocks -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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