Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752219Ab3ILCKQ (ORCPT ); Wed, 11 Sep 2013 22:10:16 -0400 Received: from mail-lb0-f179.google.com ([209.85.217.179]:32851 "EHLO mail-lb0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751433Ab3ILCKO (ORCPT ); Wed, 11 Sep 2013 22:10:14 -0400 MIME-Version: 1.0 In-Reply-To: <1378805550-29949-28-git-send-email-mgorman@suse.de> References: <1378805550-29949-1-git-send-email-mgorman@suse.de> <1378805550-29949-28-git-send-email-mgorman@suse.de> Date: Thu, 12 Sep 2013 10:10:13 +0800 Message-ID: Subject: Re: [PATCH 27/50] mm: numa: Scan pages with elevated page_mapcount From: Hillf Danton To: Mel Gorman Cc: Peter Zijlstra , Rik van Riel , Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1842 Lines: 40 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? > - /* > * Rate-limit the amount of data that is being migrated to a node. > * Optimal placement is no good if the memory bus is saturated and > * all the time is being spent migrating! -- 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/