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 61D806B0012 for ; Wed, 15 Jun 2011 21:50:44 -0400 (EDT) Received: from mail-ww0-f45.google.com (mail-ww0-f45.google.com [74.125.82.45]) (authenticated bits=0) by smtp1.linux-foundation.org (8.14.2/8.13.5/Debian-3ubuntu1.1) with ESMTP id p5G1od8H020365 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=FAIL) for ; Wed, 15 Jun 2011 18:50:40 -0700 Received: by wwi36 with SMTP id 36so883158wwi.26 for ; Wed, 15 Jun 2011 18:50:38 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1308173849.15315.91.camel@twins> References: <1308097798.17300.142.camel@schen9-DESK> <1308101214.15392.151.camel@sli10-conroe> <1308138750.15315.62.camel@twins> <20110615161827.GA11769@tassilo.jf.intel.com> <1308156337.2171.23.camel@laptop> <1308163398.17300.147.camel@schen9-DESK> <1308169937.15315.88.camel@twins> <4DF91CB9.5080504@linux.intel.com> <1308172336.17300.177.camel@schen9-DESK> <1308173849.15315.91.camel@twins> From: Linus Torvalds Date: Wed, 15 Jun 2011 18:50:18 -0700 Message-ID: Subject: Re: REGRESSION: Performance regressions from switching anon_vma->lock to mutex Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra , Tim Chen Cc: Andi Kleen , Shaohua Li , Andrew Morton , Hugh Dickins , KOSAKI Motohiro , Benjamin Herrenschmidt , David Miller , Martin Schwidefsky , Russell King , Paul Mundt , Jeff Dike , Richard Weinberger , "Luck, Tony" , KAMEZAWA Hiroyuki , Mel Gorman , Nick Piggin , Namhyung Kim , "Shi, Alex" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "Rafael J. Wysocki" On Wed, Jun 15, 2011 at 2:37 PM, Peter Zijlstra wrote: > > http://programming.kicks-ass.net/sekrit/39-2.txt.bz2 > http://programming.kicks-ass.net/sekrit/tip-2.txt.bz2 > > tip+sirq+linus is still slightly faster than .39 here, Hmm. Your profile doesn't show the mutex slowpath at all, so there's a big difference to the one Tim quoted parts of. In fact, your profile looks fine. The load clearly spends tons of time in page faulting and in timing things (that read_hpet thing is disgusting), but with that in mind, the profile doesn't look scary. Yes, the 2% spinlock time is bad, but you've clearly not hit the real lock contention case. The mutex lock shows up, but _way_ below the spinlock, and the slowpath never shows at all. You end up having mutex_spin_on_owner at 0.09%, it's not really visible. Clearly going from your two-socket 12-core thing to Tim's four-socket 40-core case is a big jump. But maybe it really was about RCU, and even the limited softirq patch that moves the grace period stuff etc back to softirqs ends up helping. Tim, have you tried running your bigger load with that patch? You could try my patch on top too just to match Peter's tree, but I doubt that's the big first-order issue. 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org