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Date: Mon, 1 Jul 2013 00:00:04 +0200 From: Borislav Petkov <bp@...en8.de> To: Wedson Almeida Filho <wedsonaf@...il.com> Cc: Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl> Subject: Re: [PATCH] x86: Use asm-goto to implement mutex fast path on x86-64 On Sat, Jun 29, 2013 at 04:56:30PM -0700, Wedson Almeida Filho wrote: > On Fri, Jun 28, 2013 at 7:09 AM, Borislav Petkov <bp@...en8.de> wrote: > > > Btw, do we have any perf data showing any improvements from this patch? > > I wrote a simple test the measures the time it takes to acquire and > release an uncontended mutex (i.e., we always take the fast path) > 100k times. I ran it a few times, the original code averages > 2.743436ms, and the new code averages 2.101098ms, so it's about 23% improvement. Microbenchmark results tend to be misleading in such situations. Rather, it would be much closer to reality if you traced a real workload like a simple kernel build, for example, with and without your patch. I.e., something like perf stat --repeat 5 ./build-kernel.sh and take a look at what the perfcouters are saying in both cases. > I also think the code looks cleaner this way. No doubt. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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