From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4639DBEC.2020401@yahoo.com.au> Date: Thu, 03 May 2007 22:56:12 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: 2.6.22 -mm merge plans -- vm bugfixes References: <20070430162007.ad46e153.akpm@linux-foundation.org> <4636FDD7.9080401@yahoo.com.au> <4638009E.3070408@yahoo.com.au> <46393BA7.6030106@yahoo.com.au> <20070503103756.GA19958@infradead.org> In-Reply-To: <20070503103756.GA19958@infradead.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Hellwig Cc: Hugh Dickins , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli List-ID: Christoph Hellwig wrote: > On Thu, May 03, 2007 at 11:32:23AM +1000, Nick Piggin wrote: > >>The attached patch gets performance up a bit by avoiding some >>barriers and some cachelines: >> >>G5 >> pagefault fork exec >>2.6.21 1.49-1.51 164.6-170.8 741.8-760.3 >>+patch 1.71-1.73 175.2-180.8 780.5-794.2 >>+patch2 1.61-1.63 169.8-175.0 748.6-757.0 >> >>So that brings the fork/exec hits down to much less than 5%, and >>would likely speed up other things that lock the page, like write >>or page reclaim. > > > Is that every fork/exec or just under certain cicumstances? > A 5% regression on every fork/exec is not acceptable. Well after patch2, G5 fork is 3% and exec is 1%, I'd say the P4 numbers will be improved as well with that patch. Then if we have specific lock/unlock bitops, I hope it should reduce that further. The overhead that is there should just be coming from the extra overhead in the file backed fault handler. For noop fork/execs, I think that tends to be more pronounced, it is hard to see any difference on any non-micro benchmark. The other thing is that I think there could be some cache effects happening -- for example the exec numbers on the 2nd line are disproportionately large. It definitely isn't a good thing to drop performance anywhere though, so I'll keep looking for improvements. -- SUSE Labs, Novell Inc. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org