linux-kernel - Re: lmbench lat_mmap slowdown with CONFIG

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Date:	Wed, 21 Jan 2009 14:23:13 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Nick Piggin <npiggin@...e.de>
CC:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>, hpa@...or.com,
	jeremy@...source.com, chrisw@...s-sol.org, zach@...are.com,
	rusty@...tcorp.com.au, Andrew Morton <akpm@...ux-foundation.org>,
	Xen-devel <xen-devel@...ts.xensource.com>
Subject: Re: lmbench lat_mmap slowdown with CONFIG_PARAVIRT

Nick Piggin wrote:
> Oh, _llc_ references/misses? Ouch.
>
> You have, what 32K L1I, 32K L1D, and 4MB L2? And even this microbenchmark
> is seeing increased L2 misses by nearly 3%. Hmm, I wonder where that is
> coming from? Instruction fetches?
>   

I assume so.  There should be no extra data accesses with 
CONFIG_PARAVIRT (hm, there's probably some extra stack/spill traffic, 
but I surely hope that's not falling out of cache).

    J
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