Date: Fri, 21 Sep 2018 12:27:36 +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: r338853 - head/sys/amd64/amd64 Message-ID: <201809211227.w8LCRaqe025154@repo.freebsd.org>
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Author: mjg Date: Fri Sep 21 12:27:36 2018 New Revision: 338853 URL: https://svnweb.freebsd.org/changeset/base/338853 Log: amd64: check for small size in memmove, memcpy and memset If the size is 15 bytes or less avoid spinning up rep just to copy the 8 bytes. In my tests on EPYC and old Intel microarchs without ERMS (like Westmere) it provided a nice win over the current version (e.g. for EPYC memset with 15 bytes of size goes from 59712651 ops/s to 70600095) all while almost not pessimizing the other cases. Data collected during package building shows that < 16 sizes are pretty common. Verified with the glibc test suite. Approved by: re (kib) Modified: head/sys/amd64/amd64/support.S Modified: head/sys/amd64/amd64/support.S ============================================================================== --- head/sys/amd64/amd64/support.S Fri Sep 21 09:27:32 2018 (r338852) +++ head/sys/amd64/amd64/support.S Fri Sep 21 12:27:36 2018 (r338853) @@ -116,6 +116,8 @@ ENTRY(memmove_std) cmpq %rcx,%r8 /* overlapping && src < dst? */ jb 2f + cmpq $15,%rcx + jbe 1f shrq $3,%rcx /* copy by 64-bit words */ rep movsq @@ -124,6 +126,7 @@ ENTRY(memmove_std) jne 1f POP_FRAME_POINTER ret + ALIGN_TEXT 1: rep movsb @@ -191,6 +194,8 @@ ENTRY(memcpy_std) PUSH_FRAME_POINTER movq %rdi,%rax movq %rdx,%rcx + cmpq $15,%rcx + jbe 1f shrq $3,%rcx /* copy by 64-bit words */ rep movsq @@ -199,6 +204,7 @@ ENTRY(memcpy_std) jne 1f POP_FRAME_POINTER ret + ALIGN_TEXT 1: rep movsb @@ -227,6 +233,8 @@ ENTRY(memset_std) movzbq %sil,%r8 movabs $0x0101010101010101,%rax imulq %r8,%rax + cmpq $15,%rcx + jbe 1f shrq $3,%rcx rep stosq @@ -236,6 +244,7 @@ ENTRY(memset_std) movq %r9,%rax POP_FRAME_POINTER ret + ALIGN_TEXT 1: rep stosb
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