From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755925Ab1KNSrq (ORCPT ); Mon, 14 Nov 2011 13:47:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36404 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752617Ab1KNSrp (ORCPT ); Mon, 14 Nov 2011 13:47:45 -0500 Date: Mon, 14 Nov 2011 13:47:17 -0500 From: Dave Jones To: Johannes Weiner Cc: Andrea Arcangeli , Mel Gorman , Jan Kara , Andy Isaacson , linux-kernel@vger.kernel.org, linux-mm@vger.kernel.org, kernel-team@fedoraproject.org Subject: Re: long sleep_on_page delays writing to slow storage Message-ID: <20111114184717.GA7006@redhat.com> Mail-Followup-To: Dave Jones , Johannes Weiner , Andrea Arcangeli , Mel Gorman , Jan Kara , Andy Isaacson , linux-kernel@vger.kernel.org, linux-mm@vger.kernel.org, kernel-team@fedoraproject.org References: <20111107045928.GK8927@hexapodia.org> <20111109170027.GB7495@quack.suse.cz> <20111109175201.GB3083@suse.de> <20111109180646.GM5075@redhat.com> <20111110093442.GG3153@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111110093442.GG3153@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 10, 2011 at 10:34:42AM +0100, Johannes Weiner wrote: > > I wonder if a change like this would be enough? > > > > sync_migration = !(gfp_mask & __GFP_NO_KSWAPD); > > > > But even if hidden in a new function, the main downside overall is the > > fact we'll pass one more var through the stack of fast paths. > > > > Johannes I recall you reported this too and Mel suggested the above > > change, did it help in the end? > > Yes, it completely fixed the latency problem. > > That said, I haven't looked at the impact on the THP success rate, but > a regression there is probably less severe than half-minute-stalls in > interactive applications. FWIW, we've had a few reports from Fedora users since we moved to 3.x kernels about similar problems, so whatever the fix is for this should probably go to stable too. I could push an update for Fedora users to test the change above if that would be helpful ? Dave