Messages in this thread | | | Date | Fri, 12 Oct 2012 20:04:11 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register |
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On Fri, Oct 12, 2012 at 09:07:43AM +0000, Ma, Ling wrote: > > > > So is that also true for AMD CPUs? > > > Although Bulldozer put 32byte instruction into decoupled 16byte entry > > > buffers, it still decode 4 instructions per cycle, so 4 instructions > > > will be fed into execution unit and > > > 2 loads ,1 write will be issued per cycle. > > > > I'd be very interested with what benchmarks are you seeing that perf > > improvement on Atom and who knows, maybe I could find time to run them > > on Bulldozer and see how your patch behaves there :-).M > I use another benchmark from gcc, there are many code, and extract > one simple benchmark, you may use it to test (cc -o copy_page > copy_page.c), my initial result shows new copy page version is still > better on bulldozer machine, because the machine is first release, > please verify result. And CC to Ian.
Right, so benchmark shows around 20% speedup on Bulldozer but this is a microbenchmark and before pursue this further, we need to verify whether this brings any palpable speedup with a real benchmark, I don't know, kernbench, netbench, whatever. Even something as boring as kernel build. And probably check for perf regressions on the rest of the uarches.
Thanks.
-- Regards/Gruss, Boris.
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