From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 0B7826B031D for ; Fri, 20 Aug 2010 06:24:01 -0400 (EDT) Date: Fri, 20 Aug 2010 18:23:55 +0800 From: Wu Fengguang Subject: Re: compaction: trying to understand the code Message-ID: <20100820102355.GE8440@localhost> References: <325E0A25FE724BA18190186F058FF37E@rainbow> <20100817111018.GQ19797@csn.ul.ie> <4385155269B445AEAF27DC8639A953D7@rainbow> <20100818154130.GC9431@localhost> <565A4EE71DAC4B1A820B2748F56ABF73@rainbow> <20100819160006.GG6805@barrios-desktop> <20100820053447.GA13406@localhost> <20100820093558.GG19797@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100820093558.GG19797@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Iram Shahzad , Minchan Kim , "linux-mm@kvack.org" , KOSAKI Motohiro List-ID: On Fri, Aug 20, 2010 at 05:35:59PM +0800, Mel Gorman wrote: > On Fri, Aug 20, 2010 at 01:34:47PM +0800, Wu Fengguang wrote: > > You do run lots of tasks: kernel_stack=1880kB. > > > > And you have lots of free memory, page reclaim has never run, so > > inactive_anon=0. This is where compaction is different from vmscan. > > In vmscan, inactive_anon is reasonably large, and will only be > > compared directly with isolated_anon. > > > > True, the key observation here was that compaction is being run via the > proc trigger. Normally it would be run as part of the direct reclaim > path when kswapd would already be awake. too_many_isolated() needs to be > different for compaction to take the whole system into account. What > would be the best alternative? Here is one possibility. A reasonable > alternative would be that when inactive < active that isolated can't be > more than num_online_cpus() * 2 (i.e. one compactor per online cpu). > > diff --git a/mm/compaction.c b/mm/compaction.c > index 94cce51..1e000b7 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -215,14 +215,16 @@ static void acct_isolated(struct zone *zone, struct compact_control *cc) > static bool too_many_isolated(struct zone *zone) > { > > - unsigned long inactive, isolated; > + unsigned long active, inactive, isolated; > > + active = zone_page_state(zone, NR_ACTIVE_FILE) + > + zone_page_state(zone, NR_INACTIVE_ANON); s/NR_INACTIVE_ANON/NR_ACTIVE_ANON/ > inactive = zone_page_state(zone, NR_INACTIVE_FILE) + > zone_page_state(zone, NR_INACTIVE_ANON); > isolated = zone_page_state(zone, NR_ISOLATED_FILE) + > zone_page_state(zone, NR_ISOLATED_ANON); > > - return isolated > inactive; > + return (inactive > active) ? isolated > inactive : false; Note that for anon LRU, inactive_ratio may be large numbers. (inactive > active) is not easy, and not stable even when inactive_ratio=1. 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