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Message-ID: <20091113073340.GA26127@elte.hu> Date: Fri, 13 Nov 2009 08:33:40 +0100 From: Ingo Molnar <mingo@...e.hu> To: Pavel Machek <pavel@....cz> Cc: "H. Peter Anvin" <hpa@...or.com>, "Ma, Ling" <ling.ma@...el.com>, Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH RFC] [X86] performance improvement for memcpy_64.S by fast string. * Pavel Machek <pavel@....cz> wrote: > > Ling, if you are interested, could you send a user-space test-app to > > this thread that everyone could just compile and run on various older > > boxes, to gather a performance profile of hand-coded versus string ops > > performance? > > > > ( And i think we can make a judgement based on cache-hot performance > > alone - if then the strings ops will perform comparatively better in > > cache-cold scenarios, so the cache-hot numbers would be a conservative > > estimate. ) > > Ugh, really? I'd expect cache-cold performance to be not helped at all > (memory bandwidth limit) and you'll get slow down from additional > i-cache misses... That's my point - the new code is shorter, which will run comparatively faster in a cache-cold environment. Ingo -- 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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