From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx126.postini.com [74.125.245.126]) by kanga.kvack.org (Postfix) with SMTP id D055F6B0032 for ; Mon, 17 Jun 2013 18:27:43 -0400 (EDT) Subject: Re: Performance regression from switching lock to rw-sem for anon-vma tree From: Tim Chen In-Reply-To: References: <1371165333.27102.568.camel@schen9-DESK> <1371167015.1754.14.camel@buesod1.americas.hpqcorp.net> <1371226197.27102.594.camel@schen9-DESK> <1371249104.1758.20.camel@buesod1.americas.hpqcorp.net> Content-Type: text/plain; charset="UTF-8" Date: Mon, 17 Jun 2013 15:27:46 -0700 Message-ID: <1371508066.27102.639.camel@schen9-DESK> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michel Lespinasse Cc: Davidlohr Bueso , Ingo Molnar , Rik van Riel , Peter Zijlstra , Andrea Arcangeli , Mel Gorman , "Shi, Alex" , Andi Kleen , Andrew Morton , "Wilcox, Matthew R" , Dave Hansen , linux-kernel@vger.kernel.org, linux-mm On Fri, 2013-06-14 at 15:47 -0700, Michel Lespinasse wrote: > On Fri, Jun 14, 2013 at 3:31 PM, Davidlohr Bueso wrote: > > A few ideas that come to mind are avoiding taking the ->wait_lock and > > avoid dealing with waiters when doing the optimistic spinning (just like > > mutexes do). > > > > I agree that we should first deal with the optimistic spinning before > > adding the MCS complexity. > > Maybe it would be worth disabling the MCS patch in mutex and comparing > that to the rwsem patches ? Just to make sure the rwsem performance > delta isn't related to that. > I've tried to back out the MCS patch. In fact, for exim, it is about 1% faster without MCS. So the better performance of mutex I saw was not due to MCS. Thanks for the suggestion. Tim -- 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