From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx168.postini.com [74.125.245.168]) by kanga.kvack.org (Postfix) with SMTP id BF7146B006E for ; Tue, 19 Jun 2012 14:29:43 -0400 (EDT) Message-ID: <4FE0C514.4040807@jp.fujitsu.com> Date: Tue, 19 Jun 2012 14:29:40 -0400 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH V5 4/5] mm, vmscan: fix do_try_to_free_pages() livelock References: <1340038051-29502-1-git-send-email-yinghan@google.com> <1340038051-29502-4-git-send-email-yinghan@google.com> In-Reply-To: <1340038051-29502-4-git-send-email-yinghan@google.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: yinghan@google.com Cc: mhocko@suse.cz, hannes@cmpxchg.org, mel@csn.ul.ie, kamezawa.hiroyu@jp.fujitsu.com, riel@redhat.com, dhillf@gmail.com, hughd@google.com, dan.magenheimer@oracle.com, akpm@linux-foundation.org, linux-mm@kvack.org, kosaki.motohiro@jp.fujitsu.com On 6/18/2012 12:47 PM, Ying Han wrote: > Currently, do_try_to_free_pages() can enter livelock. Because of, > now vmscan has two conflicted policies. > > 1) kswapd sleep when it couldn't reclaim any page even though > reach priority 0. This is because to avoid kswapd() infinite > loop. That said, kswapd assume direct reclaim makes enough > free pages either regular page reclaim or oom-killer. > This logic makes kswapd -> direct-reclaim dependency. > 2) direct reclaim continue to reclaim without oom-killer until > kswapd turn on zone->all_unreclaimble. This is because > to avoid too early oom-kill. > This logic makes direct-reclaim -> kswapd dependency. > > In worst case, direct-reclaim may continue to page reclaim forever > when kswapd is slept and any other thread don't wakeup kswapd. > > We can't turn on zone->all_unreclaimable because this is racy. > direct reclaim path don't take any lock. Thus this patch removes > zone->all_unreclaimable field completely and recalculates every > time. > > Note: we can't take the idea that direct-reclaim see zone->pages_scanned > directly and kswapd continue to use zone->all_unreclaimable. Because, > it is racy. commit 929bea7c71 (vmscan: all_unreclaimable() use > zone->all_unreclaimable as a name) describes the detail. > > Reported-by: Aaditya Kumar > Reported-by: Ying Han > Signed-off-by: KOSAKI Motohiro > Acked-by: Rik van Riel Please drop this. I've got some review comment about this patch and i need respin. but thank you for paying attention this. -- 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/ . Don't email: email@kvack.org