From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 30 Jul 2007 17:20:07 -0700 From: Andrew Morton Subject: Re: [rfc] [patch] mm: zone_reclaim fix for pseudo file systems Message-Id: <20070730172007.ddf7bdee.akpm@linux-foundation.org> In-Reply-To: <20070731000138.GA32468@localdomain> References: <20070727232753.GA10311@localdomain> <20070730132314.f6c8b4e1.akpm@linux-foundation.org> <20070731000138.GA32468@localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Ravikiran G Thirumalai Cc: linux-mm@kvack.org, Christoph Lameter , shai@scalex86.org List-ID: On Mon, 30 Jul 2007 17:01:38 -0700 Ravikiran G Thirumalai wrote: > >The (cheesy) way in which reclaim currently handles this sort of thing is > >to scan like mad, then to eventually set zone->all_unreclaimable. Once > >that has been set, the kernel will reduce the amount of scanning effort it > >puts into that zone by a very large amount. If the zone later comes back > >to life, all_unreclaimable gets cleared and things proceed as normal. > > I see. But this obviously does not work in this case. I have noticed the > process getting into 'system' and staying there for hours. I have never > noticed the app complete. Perhaps because I did not wait long enough. > So do you think a more aggressive auto setting/unsetting of 'all_unreclaimable' > is a better approach? The problem is that __zone_reclaim() doesn't use all_unreclaimable at all. You'll note that all the other callers of shrink_zone() do take avoiding action if the zone is in all_unreclaimable state, but __zone_reclaim() forgot to. Fixing that could/should fix your CPU consumption problem. It will further propagate the existing lameness, but replacing all_unreclaimable with something more efficient, more accurate and more complex is a separate problem. -- 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