From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id B2D3F6B01C3 for ; Tue, 23 Mar 2010 14:00:17 -0400 (EDT) Date: Tue, 23 Mar 2010 19:00:02 +0100 From: Ingo Molnar Subject: Re: [Bugme-new] [Bug 15618] New: 2.6.18->2.6.32->2.6.33 huge regression in performance Message-ID: <20100323180002.GA2965@elte.hu> References: <20100323102208.512c16cc.akpm@linux-foundation.org> <20100323173409.GA24845@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Linus Torvalds Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org, ant.starikov@gmail.com, Peter Zijlstra List-ID: * Linus Torvalds wrote: > On Tue, 23 Mar 2010, Ingo Molnar wrote: > > > > It shows a very brutal amount of page fault invoked mmap_sem spinning > > overhead. > > Isn't this already fixed? It's the same old "x86-64 rwsemaphores are using > the shit-for-brains generic version" thing, and it's fixed by > > 1838ef1 x86-64, rwsem: 64-bit xadd rwsem implementation > 5d0b723 x86: clean up rwsem type system > 59c33fa x86-32: clean up rwsem inline asm statements Ah, indeed! > NOTE! None of those are in 2.6.33 - they were merged afterwards. But they > are in 2.6.34-rc1 (and obviously current -git). So Anton would have to > compile his own kernel to test his load. another option is to run the rawhide kernel via something like: yum update --enablerepo=development kernel this will give kernel-2.6.34-0.13.rc1.git1.fc14.x86_64, which has those changes included. OTOH that kernel has debugging [lockdep] enabled so it might not be comparable. > We could mark them as stable material if the load in question is a real load > rather than just a test-case. On one of the random page-fault benchmarks the > rwsem fix was something like a 400% performance improvement, and it was > apparently visible in real life on some crazy SGI "initialize huge heap > concurrently on lots of threads" load. > > Side note: the reason the spinlock sucks is because of the fair ticket > locks, it really does all the wrong things for the rwsem code. That's why > old kernels don't show it - the old unfair locks didn't show the same kind > of behavior. Yeah. Ingo -- 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