Messages in this thread | | | From | Andrew Lutomirski <> | Date | Mon, 15 Aug 2011 16:08:19 -0400 | Subject | Re: x86 memcpy performance |
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On Mon, Aug 15, 2011 at 4:05 PM, Borislav Petkov <bp@alien8.de> wrote: > On Mon, Aug 15, 2011 at 03:11:40PM -0400, Andrew Lutomirski wrote: >> > Well, copy_from_user... does a bunch of rep; movsq - if the SSE version >> > shows reasonable speedup there, we might need to make those work too. >> >> I'm a little surprised that SSE beats fast string operations, but I >> guess benchmarking always wins. > > If by fast string operations you mean X86_FEATURE_ERMS, then that's > Intel-only and that actually would need to be benchmarked separately. > Currently, I see speedup for large(r) buffers only vs rep; movsq. But I > dunno about rep; movsb's enhanced rep string tricks Intel does.
I meant X86_FEATURE_REP_GOOD. (That may also be Intel-only, but it sounds like rep;movsq might move whole cachelines on cpus at least a few generations back.) I don't know if any ERMS cpus exist yet.
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