Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752584Ab3FQW1o (ORCPT ); Mon, 17 Jun 2013 18:27:44 -0400 Received: from mga02.intel.com ([134.134.136.20]:57231 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751126Ab3FQW1n (ORCPT ); Mon, 17 Jun 2013 18:27:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,884,1363158000"; d="scan'208";a="331138158" Subject: Re: Performance regression from switching lock to rw-sem for anon-vma tree From: Tim Chen 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 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 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1035 Lines: 25 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/