From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753405AbcEWXlJ (ORCPT ); Mon, 23 May 2016 19:41:09 -0400 Received: from mail-pa0-f44.google.com ([209.85.220.44]:36742 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751675AbcEWXlH (ORCPT ); Mon, 23 May 2016 19:41:07 -0400 Date: Mon, 23 May 2016 16:32:56 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: Michal Hocko , Vlastimil Babka , David Rientjes , Mel Gorman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch] mm, migrate: increment fail count on ENOMEM In-Reply-To: <20160523150202.70702708ce323b36ad94cbab@linux-foundation.org> Message-ID: References: <20160520130649.GB5197@dhcp22.suse.cz> <573F0ED0.4010908@suse.cz> <20160520133121.GB5215@dhcp22.suse.cz> <20160523150202.70702708ce323b36ad94cbab@linux-foundation.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 23 May 2016, Andrew Morton wrote: > On Fri, 20 May 2016 15:31:21 +0200 Michal Hocko wrote: > > On Fri 20-05-16 15:19:12, Vlastimil Babka wrote: > > > On 05/20/2016 03:06 PM, Michal Hocko wrote: > > [...] > > > > Why don't we need also to count also retries? > > > > > > We could, but not like you suggest. > > > > > > > --- > > > > 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; > > > > > > This overwrites rc == -ENOMEM, which at least compaction needs to recognize. > > > But we could duplicate "nr_failed += retry" in the case -ENOMEM. > > > > Right you are. So we should do > > --- > > diff --git a/mm/migrate.c b/mm/migrate.c > > index 53ab6398e7a2..123fed94022b 100644 > > --- 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 += retry + 1; > > goto out; > > case -EAGAIN: > > retry++; > > > > > > argh, this was lost. Please resend as a real patch sometime? It's not correct. "retry" is reset to 0 each time around the loop, and it's only a meaningful number to add on to nr_failed, in the case when we've gone through the whole list: not in this "goto out" case. We could add another loop to count how many are left when we hit -ENOMEM, and add that on to nr_failed; but I'm not convinced that it's worth the bother. Hugh