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Message-Id: <200807301653.10154.rusty@rustcorp.com.au> Date: Wed, 30 Jul 2008 16:53:09 +1000 From: Rusty Russell <rusty@...tcorp.com.au> To: Nick Piggin <nickpiggin@...oo.com.au> Cc: lguest <lguest@...abs.org>, linux-kernel@...r.kernel.org, "kvm-devel" <kvm-devel@...ts.sourceforge.net> Subject: Re: [PATCH 2/2] lguest: use get_user_pages_fast() instead of get_user_pages() On Wednesday 30 July 2008 15:30:10 Nick Piggin wrote: > On Wednesday 30 July 2008 14:39, Rusty Russell wrote: > > Before: 5.93 seconds > > After: 5.40 seconds > > > > (Counts of slow vs fastpath in this usage are 6092 and 2852462 > > respectively.) > > > > And more importantly for lguest, the code is simpler. > > Cool. That's actually a fairly significant straight-line performance > improvement, given that the lguest processes are running one-at-a-time > right? (and not contending on the locks or bouncing cachelines too much) Yep. I mean, the performance is abysmal either way (native for this is about 10x faster), but it would be interesting to see kvm numbers as they have a more sophisticated shadow page table setup. Not as trivial as lguest since they seem to use the mm sem to protect other things... Cheers, Rusty. -- 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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