Author: mjg Date: Thu Sep 6 19:42:40 2018 New Revision: 338508 URL: https://svnweb.freebsd.org/changeset/base/338508
Log: amd64: depessimize copyinstr_smap The stac/clac combo around each byte copy is causing a measurable slowdown in benchmarks. Do it only before and after all data is copied. While here reorder the code to avoid a forward branch in the common case. Note the copying loop (originating from copyinstr) is avoidably slow and will be fixed later. Reviewed by: kib Approved by: re (gjb) Differential Revision: https://reviews.freebsd.org/D17063 Modified: head/sys/amd64/amd64/support.S Modified: head/sys/amd64/amd64/support.S ============================================================================== --- head/sys/amd64/amd64/support.S Thu Sep 6 19:28:52 2018 (r338507) +++ head/sys/amd64/amd64/support.S Thu Sep 6 19:42:40 2018 (r338508) @@ -914,6 +914,8 @@ ENTRY(copyinstr_smap) subq %rsi,%rax jbe cpystrflt + stac + /* restrict maxlen to <= VM_MAXUSER_ADDRESS-from */ cmpq %rdx,%rax jae 1f @@ -924,32 +926,20 @@ ENTRY(copyinstr_smap) 2: decq %rdx - jz copyinstr_toolong + jz copyinstr_toolong_smap - stac lodsb stosb - clac orb %al,%al jnz 2b + clac + copyinstr_succ: /* Success -- 0 byte reached */ decq %rdx xorl %eax,%eax - jmp cpystrflt_x -copyinstr_toolong: - /* rdx is zero - return ENAMETOOLONG or EFAULT */ - movq $VM_MAXUSER_ADDRESS,%rax - cmpq %rax,%rsi - jae cpystrflt - movq $ENAMETOOLONG,%rax - jmp cpystrflt_x - /* Fault entry clears PSL.AC */ -cpystrflt: - movq $EFAULT,%rax - cpystrflt_x: /* set *lencopied and return %eax */ movq PCPU(CURPCB),%rcx @@ -962,6 +952,21 @@ cpystrflt_x: 1: POP_FRAME_POINTER ret + /* Fault entry clears PSL.AC */ +cpystrflt: + movq $EFAULT,%rax + jmp cpystrflt_x + +copyinstr_toolong_smap: + clac +copyinstr_toolong: + /* rdx is zero - return ENAMETOOLONG or EFAULT */ + movq $VM_MAXUSER_ADDRESS,%rax + cmpq %rax,%rsi + jae cpystrflt + movq $ENAMETOOLONG,%rax + jmp cpystrflt_x + END(copyinstr_smap) /* _______________________________________________ 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"
