Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752307Ab1DZIrX (ORCPT ); Tue, 26 Apr 2011 04:47:23 -0400 Received: from mail-ww0-f42.google.com ([74.125.82.42]:43484 "EHLO mail-ww0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751774Ab1DZIrV convert rfc822-to-8bit (ORCPT ); Tue, 26 Apr 2011 04:47:21 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=vOwyhfefNXDT46A09nI+FXimlgJRL1gADj9gomuAJqBQ2QHFz912qPeJftv4+l50et Ga4QG6ePc2uU2WG0GNPlgPIXmGz+80sO44tcdu6DKlRlqNNY/UGOP6CWw6EDRQ0Oe57c MSTrK8JwyeMQFSKPGDwwjJ7sDdJjf8u0rwP1o= MIME-Version: 1.0 In-Reply-To: <20110426162438.F393.A69D9226@jp.fujitsu.com> References: <20110426154037.F38B.A69D9226@jp.fujitsu.com> <20110426162438.F393.A69D9226@jp.fujitsu.com> Date: Tue, 26 Apr 2011 16:47:19 +0800 Message-ID: Subject: Re: [PATCH 1/2] virtio_balloon: disable oom killer when fill balloon From: Dave Young To: KOSAKI Motohiro Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2649 Lines: 76 On Tue, Apr 26, 2011 at 3:22 PM, KOSAKI Motohiro wrote: >> On Tue, Apr 26, 2011 at 2:38 PM, KOSAKI Motohiro >> wrote: >> >> When memory pressure is high, virtio ballooning will probably cause oom killing. >> >> Even if alloc_page with GFP_NORETRY itself does not directly trigger oom it >> >> will make memory becoming low then memory alloc of other processes will trigger >> >> oom killing. It is not desired behaviour. >> >> >> >> Here disable oom killer in fill_balloon to address this issue. >> >> >> >> Signed-off-by: Dave Young >> >> --- >> >>  drivers/virtio/virtio_balloon.c |    3 +++ >> >>  1 file changed, 3 insertions(+) >> >> >> >> --- linux-2.6.orig/drivers/virtio/virtio_balloon.c    2010-10-13 10:14:38.000000000 +0800 >> >> +++ linux-2.6/drivers/virtio/virtio_balloon.c 2011-04-26 11:38:43.979785141 +0800 >> >> @@ -25,6 +25,7 @@ >> >>  #include >> >>  #include >> >>  #include >> >> +#include >> >> >> >>  struct virtio_balloon >> >>  { >> >> @@ -102,6 +103,7 @@ static void fill_balloon(struct virtio_b >> >>       /* We can only do one array worth at a time. */ >> >>       num = min(num, ARRAY_SIZE(vb->pfns)); >> >> >> >> +     oom_killer_disable(); >> > >> > I think this patch need proper comment at least. My first impression >> > is, "Hm, __GFP_NORETRY should prevent oom, why is this necessary?". >> > So, this actually prevent _another_ thread call out_of_memory(). >> >> Thanks, will fix. >> >> > Also, Here doesn't have any exclusion against hibernation (ie another >> > oom_killer_disable() callsite). It should be described why lock is >> > unnecessary. >> >> Good catch, but lock should better be handled in oom_killer_disable >> function itself, >> What do you think? >> >> For oom killer multi user there's more problem, if process A disable >> oom killer then Process B enable oom killer, it is not A want to see, >> Any thoughts? > > If baloon and hibernation don't have any implicit exclusion, you are > right. For this case, hibernation will freeze balloon thread before call oom_killer_disable, so there's no problem. If we consider future users of oom_killer_disabled, we will have to deal with it. > > Sorry, I don't virtio internal. please don't ask me. > > > > -- Regards dave -- 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/