From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933160AbcETNGx (ORCPT ); Fri, 20 May 2016 09:06:53 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:32917 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933130AbcETNGw (ORCPT ); Fri, 20 May 2016 09:06:52 -0400 Date: Fri, 20 May 2016 15:06:49 +0200 From: Michal Hocko To: David Rientjes Cc: Andrew Morton , Vlastimil Babka , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch] mm, migrate: increment fail count on ENOMEM Message-ID: <20160520130649.GB5197@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 19-05-16 15:11:23, David Rientjes wrote: > If page migration fails due to -ENOMEM, nr_failed should still be > incremented for proper statistics. > > This was encountered recently when all page migration vmstats showed 0, > and inferred that migrate_pages() was never called, although in reality > the first page migration failed because compaction_alloc() failed to find > a migration target. > > This patch increments nr_failed so the vmstat is properly accounted on > ENOMEM. > > Signed-off-by: David Rientjes Acked-by: Michal Hocko One question though > --- > mm/migrate.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1171,6 +1171,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > > switch(rc) { > case -ENOMEM: > + nr_failed++; > goto out; > case -EAGAIN: > retry++; Why don't we need also to count also retries? --- diff --git a/mm/migrate.c b/mm/migrate.c index 53ab6398e7a2..ef9c5211ae3c 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1190,9 +1190,9 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, } } } +out: nr_failed += retry; rc = nr_failed; -out: if (nr_succeeded) count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); if (nr_failed) -- Michal Hocko SUSE Labs