Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756728AbZFHPL7 (ORCPT ); Mon, 8 Jun 2009 11:11:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754623AbZFHPLw (ORCPT ); Mon, 8 Jun 2009 11:11:52 -0400 Received: from gir.skynet.ie ([193.1.99.77]:46482 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753670AbZFHPLw (ORCPT ); Mon, 8 Jun 2009 11:11:52 -0400 Date: Mon, 8 Jun 2009 16:11:51 +0100 From: Mel Gorman To: Christoph Lameter Cc: Rik van Riel , KOSAKI Motohiro , yanmin.zhang@intel.com, Wu Fengguang , linuxram@us.ibm.com, linux-mm , LKML Subject: Re: [PATCH 1/3] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA Message-ID: <20090608151151.GI15070@csn.ul.ie> References: <1244466090-10711-1-git-send-email-mel@csn.ul.ie> <1244466090-10711-2-git-send-email-mel@csn.ul.ie> <4A2D129D.3020309@redhat.com> <20090608135433.GD15070@csn.ul.ie> <20090608143857.GG15070@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1597 Lines: 36 On Mon, Jun 08, 2009 at 10:55:55AM -0400, Christoph Lameter wrote: > On Mon, 8 Jun 2009, Mel Gorman wrote: > > > > The tmpfs pages are unreclaimable and therefore should not be on the anon > > > lru. > > > > > > > tmpfs pages can be swap-backed so can be reclaimable. Regardless of what > > list they are on, we still need to know how many of them there are if > > this patch is to be avoided. > > If they are reclaimable then why does it matter? They can be pushed out if > you configure zone reclaim to be that aggressive. > Because they are reclaimable by kswapd or normal direct reclaim but *not* reclaimable by zone_reclaim() if the zone_reclaim_mode is not configured appropriately. I briefly considered setting zone_reclaim_mode to 7 instead of 1 by default for large NUMA distances but that has other serious consequences such as paging in preference to going off-node as a default out-of-box behaviour. The point of the patch is that the heuristics that avoid the scan are not perfect. In the event they are wrong and a useless scan occurs, the response of the kernel after a useless scan should not be to uselessly scan a load more times around the LRU lists making no progress. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/