From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) by kanga.kvack.org (Postfix) with ESMTP id 0A8DF6B0031 for ; Wed, 9 Apr 2014 09:08:29 -0400 (EDT) Received: by mail-wi0-f173.google.com with SMTP id z2so8846064wiv.6 for ; Wed, 09 Apr 2014 06:08:27 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id g5si405586wjw.110.2014.04.09.06.08.24 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 09 Apr 2014 06:08:24 -0700 (PDT) Date: Wed, 9 Apr 2014 14:08:19 +0100 From: Mel Gorman Subject: Re: [PATCH 0/2] Disable zone_reclaim_mode by default Message-ID: <20140409130819.GS7292@suse.de> References: <1396910068-11637-1-git-send-email-mgorman@suse.de> <5343A494.9070707@suse.cz> <53445481.3030202@agliodbs.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <53445481.3030202@agliodbs.com> Sender: owner-linux-mm@kvack.org List-ID: To: Josh Berkus Cc: Robert Haas , Christoph Lameter , Vlastimil Babka , Andrew Morton , Andres Freund , Linux-MM , LKML , sivanich@sgi.com On Tue, Apr 08, 2014 at 03:56:49PM -0400, Josh Berkus wrote: > On 04/08/2014 03:53 PM, Robert Haas wrote: > > In an ideal world, the kernel would put the hottest pages on the local > > node and the less-hot pages on remote nodes, moving pages around as > > the workload shifts. In practice, that's probably pretty hard. > > Fortunately, it's not nearly as important as making sure we don't > > unnecessarily hit the disk, which is infinitely slower than any memory > > bank. > > Even if the kernel could do this, we would *still* have to disable it > for PostgreSQL, since our double-buffering makes our pages look "cold" > to the kernel ... as discussed. > If it's the shared mapping that is being used then automatic NUMA balancing should migrate those pages to a node local to the CPU accessing it but how well it works will partially depend on how much those accesses move around. It's independent of the zone_reclaim_mode issue. -- Mel Gorman SUSE Labs -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933170AbaDINI0 (ORCPT ); Wed, 9 Apr 2014 09:08:26 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55474 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932674AbaDINIZ (ORCPT ); Wed, 9 Apr 2014 09:08:25 -0400 Date: Wed, 9 Apr 2014 14:08:19 +0100 From: Mel Gorman To: Josh Berkus Cc: Robert Haas , Christoph Lameter , Vlastimil Babka , Andrew Morton , Andres Freund , Linux-MM , LKML , sivanich@sgi.com Subject: Re: [PATCH 0/2] Disable zone_reclaim_mode by default Message-ID: <20140409130819.GS7292@suse.de> References: <1396910068-11637-1-git-send-email-mgorman@suse.de> <5343A494.9070707@suse.cz> <53445481.3030202@agliodbs.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <53445481.3030202@agliodbs.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 Tue, Apr 08, 2014 at 03:56:49PM -0400, Josh Berkus wrote: > On 04/08/2014 03:53 PM, Robert Haas wrote: > > In an ideal world, the kernel would put the hottest pages on the local > > node and the less-hot pages on remote nodes, moving pages around as > > the workload shifts. In practice, that's probably pretty hard. > > Fortunately, it's not nearly as important as making sure we don't > > unnecessarily hit the disk, which is infinitely slower than any memory > > bank. > > Even if the kernel could do this, we would *still* have to disable it > for PostgreSQL, since our double-buffering makes our pages look "cold" > to the kernel ... as discussed. > If it's the shared mapping that is being used then automatic NUMA balancing should migrate those pages to a node local to the CPU accessing it but how well it works will partially depend on how much those accesses move around. It's independent of the zone_reclaim_mode issue. -- Mel Gorman SUSE Labs