From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758410Ab2IEK4P (ORCPT ); Wed, 5 Sep 2012 06:56:15 -0400 Received: from cantor2.suse.de ([195.135.220.15]:59394 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752072Ab2IEK4O (ORCPT ); Wed, 5 Sep 2012 06:56:14 -0400 Date: Wed, 5 Sep 2012 11:56:11 +0100 From: Mel Gorman To: Minchan Kim Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Bartlomiej Zolnierkiewicz , Marek Szyprowski , Michal Nazarewicz , Rik van Riel Subject: Re: [PATCH 2/2] mm: support MIGRATE_DISCARD Message-ID: <20120905105611.GI11266@suse.de> References: <1346832673-12512-1-git-send-email-minchan@kernel.org> <1346832673-12512-2-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1346832673-12512-2-git-send-email-minchan@kernel.org> 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 Wed, Sep 05, 2012 at 05:11:13PM +0900, Minchan Kim wrote: > This patch introudes MIGRATE_DISCARD mode in migration. > It drops *clean cache pages* instead of migration so that > migration latency could be reduced by avoiding (memcpy + page remapping). > It's useful for CMA because latency of migration is very important rather > than eviction of background processes's workingset. In addition, it needs > less free pages for migration targets so it could avoid memory reclaiming > to get free pages, which is another factor increase latency. > Bah, this was released while I was reviewing the older version. I did not read this one as closely but I see the enum problems have gone away at least. I'd still prefer if CMA had an additional helper to discard some pages with shrink_page_list() and migrate the remaining pages with migrate_pages(). That would remove the need to add a MIGRATE_DISCARD migrate mode at all. -- Mel Gorman SUSE Labs