Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756287Ab3IMIMF (ORCPT ); Fri, 13 Sep 2013 04:12:05 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43440 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755979Ab3IMIMA (ORCPT ); Fri, 13 Sep 2013 04:12:00 -0400 Date: Fri, 13 Sep 2013 09:11:57 +0100 From: Mel Gorman To: Hillf Danton Cc: Peter Zijlstra , Rik van Riel , Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML Subject: Re: [PATCH 27/50] mm: numa: Scan pages with elevated page_mapcount Message-ID: <20130913081157.GW22421@suse.de> References: <1378805550-29949-1-git-send-email-mgorman@suse.de> <1378805550-29949-28-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: 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 Content-Length: 1807 Lines: 43 On Thu, Sep 12, 2013 at 10:10:13AM +0800, Hillf Danton wrote: > Hillo Mel > > On Tue, Sep 10, 2013 at 5:32 PM, Mel Gorman wrote: > > Currently automatic NUMA balancing is unable to distinguish between false > > shared versus private pages except by ignoring pages with an elevated > > page_mapcount entirely. This avoids shared pages bouncing between the > > nodes whose task is using them but that is ignored quite a lot of data. > > > > This patch kicks away the training wheels in preparation for adding support > > for identifying shared/private pages is now in place. The ordering is so > > that the impact of the shared/private detection can be easily measured. Note > > that the patch does not migrate shared, file-backed within vmas marked > > VM_EXEC as these are generally shared library pages. Migrating such pages > > is not beneficial as there is an expectation they are read-shared between > > caches and iTLB and iCache pressure is generally low. > > > > Signed-off-by: Mel Gorman > > --- > [...] > > @@ -1658,13 +1660,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, > > int page_lru = page_is_file_cache(page); > > > > /* > > - * Don't migrate pages that are mapped in multiple processes. > > - * TODO: Handle false sharing detection instead of this hammer > > - */ > > - if (page_mapcount(page) != 1) > > - goto out_dropref; > > - > Is there rmap walk when migrating THP? > Should not be necessary for THP. -- Mel Gorman SUSE Labs -- 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/