From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <46298BE8.8020900@redhat.com> Date: Fri, 20 Apr 2007 23:58:32 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] lazy freeing of memory through MADV_FREE References: <46247427.6000902@redhat.com> <20070420135715.f6e8e091.akpm@linux-foundation.org> <462932BE.4020005@redhat.com> <20070420150618.179d31a4.akpm@linux-foundation.org> <4629524C.5040302@redhat.com> <46295F59.8000506@cosmosbay.com> In-Reply-To: <46295F59.8000506@cosmosbay.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org Return-Path: To: Eric Dumazet Cc: Andrew Morton , linux-kernel , linux-mm , shak List-ID: Eric Dumazet wrote: > Rik van Riel a A(C)crit : >> Andrew Morton wrote: >>> On Fri, 20 Apr 2007 17:38:06 -0400 >>> Rik van Riel wrote: >>> >>>> Andrew Morton wrote: >>>> >>>>> I've also merged Nick's "mm: madvise avoid exclusive mmap_sem". >>>>> >>>>> - Nick's patch also will help this problem. It could be that your >>>>> patch >>>>> no longer offers a 2x speedup when combined with Nick's patch. >>>>> >>>>> It could well be that the combination of the two is even better, >>>>> but it >>>>> would be nice to firm that up a bit. >>>> I'll test that. >>> >>> Thanks. >> >> Well, good news. >> >> It turns out that Nick's patch does not improve peak >> performance much, but it does prevent the decline when >> running with 16 threads on my quad core CPU! >> >> We _definately_ want both patches, there's a huge benefit >> in having them both. >> >> Here are the transactions/seconds for each combination: >> >> vanilla new glibc madv_free kernel madv_free + mmap_sem >> threads >> >> 1 610 609 596 545 > > 545 tps versus 610 tps for one thread ? It seems quite bad, no ? > > Could you please find an explanation for this ? I have no idea why this happens. Especially the last one, going from a write lock to a read lock on the mmap_sem should not make ANY difference whatsoever since we're running single threaded! >> 2 1032 1136 1196 1200 >> 4 1070 1128 2014 2024 >> 8 1000 1088 1665 2087 >> 16 779 1073 1310 1999 Performance with 2 database threads is way better though, and performance with 4 or more threads more than doubles... If you have an explanation on why single threaded performance went down a little on my quad core system, please let me know. Does performance suffer at all on a real UP system? -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic. -- 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