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Date: Wed, 26 Mar 2008 16:24:27 +1100 From: Paul Mackerras <paulus@...ba.org> To: Andi Kleen <andi@...stfloor.org> Cc: David Miller <davem@...emloft.net>, clameter@....com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, linux-ia64@...r.kernel.org, torvalds@...ux-foundation.org Subject: Re: larger default page sizes... Andi Kleen writes: > Paul Mackerras <paulus@...ba.org> writes: > > > > 4kB pages: 444.051s user + 34.406s system time > > 64kB pages: 419.963s user + 16.869s system time > > > > That's nearly 10% faster with 64kB pages -- on a kernel compile. > > Do you have some idea where the improvement mainly comes from? > Is it TLB misses or reduced in kernel overhead? Ok I assume both > play together but which part of the equation is more important? With the kernel configured for a 64k page size, but using 4k pages in the hardware page table, I get: 64k/4k: 441.723s user + 27.258s system time So the improvement in the user time is almost all due to the reduced TLB misses (as one would expect). For the system time, using 64k pages in the VM reduces it by about 21%, and using 64k hardware pages reduces it by another 30%. So the reduction in kernel overhead is significant but not as large as the impact of reducing TLB misses. Paul. -- 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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