Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757674Ab1DZHJK (ORCPT ); Tue, 26 Apr 2011 03:09:10 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:59487 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757264Ab1DZHJI convert rfc822-to-8bit (ORCPT ); Tue, 26 Apr 2011 03:09:08 -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=se5Dc3MpbM0exQkZAlLRM7mPTa55O6B/n3bqPyQG0UZ1E2hbImuxddz+nVWt0za1P6 HEnSIDFjyEFyyqDOE5yI06nZkpNcRr2kmLcuTNYX8BB4TG5+YhNQzExoHPKS6/f+a7pU yQ9K1Qn9kdmvkwD+yjThQEwKZtBO7n9pFXhnU= MIME-Version: 1.0 In-Reply-To: <20110426154037.F38B.A69D9226@jp.fujitsu.com> References: <20110426052916.GA11933@darkstar> <20110426154037.F38B.A69D9226@jp.fujitsu.com> Date: Tue, 26 Apr 2011 15:09:06 +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: 2914 Lines: 83 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? > > Thanks. > > >>       for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { >>               struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY | >>                                       __GFP_NOMEMALLOC | __GFP_NOWARN); >> @@ -119,6 +121,7 @@ static void fill_balloon(struct virtio_b >>               vb->num_pages++; >>               list_add(&page->lru, &vb->pages); >>       } >> +     oom_killer_enable(); >> >>       /* Didn't get any?  Oh well. */ >>       if (vb->num_pfns == 0) >> -- >> 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/ > > > > -- 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/