From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 247556B007D for ; Mon, 11 Jan 2010 23:59:11 -0500 (EST) Date: Tue, 12 Jan 2010 12:59:06 +0800 From: Wu Fengguang Subject: Re: [PATCH 4/4] mm/page_alloc : relieve zone->lock's pressure for memory free Message-ID: <20100112045906.GA30172@localhost> References: <1263184634-15447-4-git-send-email-shijie8@gmail.com> <1263191277-30373-1-git-send-email-shijie8@gmail.com> <20100111153802.f3150117.minchan.kim@barrios-desktop> <20100112094708.d09b01ea.kamezawa.hiroyu@jp.fujitsu.com> <20100112022708.GA21621@localhost> <28c262361001112005s745e5ecj9fd6ae3d0d997477@mail.gmail.com> <20100112042116.GA26035@localhost> <20100112133223.005b81ed.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100112133223.005b81ed.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Minchan Kim , Huang Shijie , "akpm@linux-foundation.org" , "mel@csn.ul.ie" , "kosaki.motohiro@jp.fujitsu.com" , "linux-mm@kvack.org" , Rik van Riel , David Rientjes , Christoph Lameter , Andrea Arcangeli List-ID: On Tue, Jan 12, 2010 at 12:32:23PM +0800, KAMEZAWA Hiroyuki wrote: > On Tue, 12 Jan 2010 12:21:16 +0800 > Wu Fengguang wrote: > > > BTW, > > > Hmm. It's not atomic as Kame pointed out. > > > > > > Now, zone->flags have several bit. > > > * ZONE_ALL_UNRECLAIMALBE > > > * ZONE_RECLAIM_LOCKED > > > * ZONE_OOM_LOCKED. > > > > > > I think this flags are likely to race when the memory pressure is high. > > > If we don't prevent race, concurrent reclaim and killing could be happened. > > > So I think reset zone->flags outside of zone->lock would make our efforts which > > > prevent current reclaim and killing invalidate. > > > > zone_set_flag()/zone_clear_flag() calls set_bit()/clear_bit() which is > > atomic. Do you mean more high level exclusion? > > > Ah, sorry, I missed that. > In my memory, this wasn't atomic ;) ...maybe recent change. > > I don't want to see atomic_ops here...So, how about making this back to be > zone->all_unreclaimable word ? > > Clearing this is not necessary to be atomic because this is cleard at every > page freeing. Yes the cost is a bit high. This was introduced by David Rientjes in commit e815af95f, let's hear opinions from him :) Thanks, Fengguang -- 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