From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx175.postini.com [74.125.245.175]) by kanga.kvack.org (Postfix) with SMTP id 6637D6B0033 for ; Fri, 13 Sep 2013 04:12:01 -0400 (EDT) Date: Fri, 13 Sep 2013 09:11:57 +0100 From: Mel Gorman 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: Sender: owner-linux-mm@kvack.org List-ID: To: Hillf Danton Cc: Peter Zijlstra , Rik van Riel , Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML 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, 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