From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id 72AF16B002D for ; Tue, 25 Oct 2011 05:10:02 -0400 (EDT) Date: Tue, 25 Oct 2011 11:09:56 +0200 From: Mel Gorman Subject: Re: [PATCH] mm: avoid livelock on !__GFP_FS allocations Message-ID: <20111025090956.GA10797@suse.de> References: <1319524789-22818-1-git-send-email-ccross@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1319524789-22818-1-git-send-email-ccross@android.com> Sender: owner-linux-mm@kvack.org List-ID: To: Colin Cross Cc: linux-kernel@vger.kernel.org, Andrew Morton , KAMEZAWA Hiroyuki , Andrea Arcangeli , David Rientjes , linux-mm@kvack.org On Mon, Oct 24, 2011 at 11:39:49PM -0700, Colin Cross wrote: > Under the following conditions, __alloc_pages_slowpath can loop > forever: > gfp_mask & __GFP_WAIT is true > gfp_mask & __GFP_FS is false > reclaim and compaction make no progress > order <= PAGE_ALLOC_COSTLY_ORDER > > These conditions happen very often during suspend and resume, > when pm_restrict_gfp_mask() effectively converts all GFP_KERNEL > allocations into __GFP_WAIT. b> > The oom killer is not run because gfp_mask & __GFP_FS is false, > but should_alloc_retry will always return true when order is less > than PAGE_ALLOC_COSTLY_ORDER. > > Fix __alloc_pages_slowpath to skip retrying when oom killer is > not allowed by the GFP flags, the same way it would skip if the > oom killer was allowed but disabled. > > Signed-off-by: Colin Cross Hi Colin, Your patch functionally seems fine. I see the problem and we certainly do not want to have the OOM killer firing during suspend. I would prefer that the IO devices would not be suspended until reclaim was completed but I imagine that would be a lot harder. That said, it will be difficult to remember why checking __GFP_NOFAIL in this case is necessary and someone might "optimitise" it away later. It would be preferable if it was self-documenting. Maybe something like this? (This is totally untested) mm/page_alloc.c | 22 ++++++++++++++++++++++ 1 files changed, 22 insertions(+), 0 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6e8ecb6..ad8f376 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -127,6 +127,20 @@ void pm_restrict_gfp_mask(void) saved_gfp_mask = gfp_allowed_mask; gfp_allowed_mask &= ~GFP_IOFS; } + +static bool pm_suspending(void) +{ + if ((gfp_allowed_mask & GFP_IOFS) == GFP_IOFS) + return false; + return true; +} + +#else + +static bool pm_suspending(void) +{ + return false; +} #endif /* CONFIG_PM_SLEEP */ #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE @@ -2207,6 +2221,14 @@ rebalance: goto restart; } + + /* + * Suspend converts GFP_KERNEL to __GFP_WAIT which can + * prevent reclaim making forward progress without + * invoking OOM. Bail if we are suspending + */ + if (pm_suspending()) + goto nopage; } /* Check if we should retry the allocation */ -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org