On 8 Feb 2021, at 19:15, Mateusz Guzik <m...@freebsd.org> wrote: > > The branch main has been updated by mjg: > > URL: > https://cgit.FreeBSD.org/src/commit/?id=af366d353b84bdc4e730f0fc563853abc338271c > > commit af366d353b84bdc4e730f0fc563853abc338271c > Author: Mateusz Guzik <m...@freebsd.org> > AuthorDate: 2021-02-08 17:01:48 +0000 > Commit: Mateusz Guzik <m...@freebsd.org> > CommitDate: 2021-02-08 19:15:21 +0000 > > amd64: implement strlen in assembly > > The C variant in libkern performs excessive branching to find the > non-zero byte instead of using the bsfq instruction. The same code > patched to use it is still slower than the routine implemented here > as the compiler keeps neglecting to perform certain optimizations > (like using leaq). > > On top of that the routine can is a starting point for copyinstr > which operates on words instead of bytes. > > Tested with glibc test suite. > > Sample results (calls/s): > > Haswell: > $(perl -e "print 'A' x 3"): > stock: 211198039 > patched:338626619 > asm: 465609618 > > $(perl -e "print 'A' x 100"): > stock: 83151997 > patched: 98285919 > asm: 120719888 > > AMD EPYC 7R32: > $(perl -e "print 'A' x 3"): > stock: 282523617 > asm: 491498172 > > $(perl -e "print 'A' x 100"): > stock: 114857172 > asm: 112082057
No Reviewed by? More than one pair of eyes on non-trivial assembly is almost always a good idea. Jess _______________________________________________ dev-commits-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/dev-commits-src-all To unsubscribe, send any mail to "dev-commits-src-all-unsubscr...@freebsd.org"
