From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx141.postini.com [74.125.245.141]) by kanga.kvack.org (Postfix) with SMTP id 1693A6B005D for ; Wed, 21 Nov 2012 17:04:58 -0500 (EST) Received: by mail-wg0-f41.google.com with SMTP id ds1so156318wgb.2 for ; Wed, 21 Nov 2012 14:04:56 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20121121171047.GA28875@gmail.com> References: <1353291284-2998-1-git-send-email-mingo@kernel.org> <20121119162909.GL8218@suse.de> <20121120060014.GA14065@gmail.com> <20121120074445.GA14539@gmail.com> <20121120090637.GA14873@gmail.com> <20121121171047.GA28875@gmail.com> From: Linus Torvalds Date: Wed, 21 Nov 2012 12:04:25 -1000 Message-ID: Subject: Re: [PATCH 00/27] Latest numa/core release, v16 Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: David Rientjes , Mel Gorman , Linux Kernel Mailing List , linux-mm , Peter Zijlstra , Paul Turner , Lee Schermerhorn , Christoph Lameter , Rik van Riel , Andrew Morton , Andrea Arcangeli , Thomas Gleixner , Johannes Weiner , Hugh Dickins On Wed, Nov 21, 2012 at 7:10 AM, Ingo Molnar wrote: > > Because scalability slowdowns are often non-linear. Only if you hold locks or have other non-cpu-private activity. Which the vsyscall code really shouldn't have. That said, it might be worth removing the "prefetchw(&mm->mmap_sem)" from the VM fault path. Partly because software prefetches have never ever worked on any reasonable hardware, and partly because it could seriously screw up things like the vsyscall stuff. I think we only turn prefetchw into an actual prefetch instruction on 3DNOW hardware. Which is the *old* AMD chips. I don't think even the Athlon does that. Anyway, it might be interesting to see a instruction-level annotated profile of do_page_fault() or whatever > So with CONFIG_NUMA_BALANCING=y we are taking a higher page > fault rate, in exchange for a speedup. The thing is, so is autonuma. And autonuma doesn't show any of these problems. Autonuma didn't need vsyscall hacks, autonuma didn't need TLB flushing optimizations, autonuma just *worked*, and in fact got big speedups when Mel did the exact same loads on that same machine, presumably with all the same issues.. Why are you ignoring that fact? Linus -- 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