Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755728Ab1EQQPQ (ORCPT ); Tue, 17 May 2011 12:15:16 -0400 Received: from cantor.suse.de ([195.135.220.2]:45900 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754053Ab1EQQPO (ORCPT ); Tue, 17 May 2011 12:15:14 -0400 Date: Tue, 17 May 2011 17:15:08 +0100 From: Mel Gorman To: akpm@linux-foundation.org Cc: Minchan Kim , Colin Ian King , James Bottomley , KOSAKI Motohiro , akpm@linux-foundation.org, raghu.prabhu13@gmail.com, jack@suse.cz, chris.mason@oracle.com, cl@linux.com, penberg@kernel.org, riel@redhat.com, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: [PATCH] mm: vmscan: Correctly check if reclaimer should schedule during shrink_slab Message-ID: <20110517161508.GN5279@suse.de> References: <1305295404-12129-5-git-send-email-mgorman@suse.de> <4DCFAA80.7040109@jp.fujitsu.com> <1305519711.4806.7.camel@mulgrave.site> <20110516084558.GE5279@suse.de> <20110516102753.GF5279@suse.de> <20110517103840.GL5279@suse.de> <1305640239.2046.27.camel@lenovo> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1305640239.2046.27.camel@lenovo> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2803 Lines: 71 It has been reported on some laptops that kswapd is consuming large amounts of CPU and not being scheduled when SLUB is enabled during large amounts of file copying. It is expected that this is due to kswapd missing every cond_resched() point because; shrink_page_list() calls cond_resched() if inactive pages were isolated which in turn may not happen if all_unreclaimable is set in shrink_zones(). If for whatver reason, all_unreclaimable is set on all zones, we can miss calling cond_resched(). balance_pgdat() only calls cond_resched if the zones are not balanced. For a high-order allocation that is balanced, it checks order-0 again. During that window, order-0 might have become unbalanced so it loops again for order-0 and returns that it was reclaiming for order-0 to kswapd(). It can then find that a caller has rewoken kswapd for a high-order and re-enters balance_pgdat() without ever calling cond_resched(). shrink_slab only calls cond_resched() if we are reclaiming slab pages. If there are a large number of direct reclaimers, the shrinker_rwsem can be contended and prevent kswapd calling cond_resched(). This patch modifies the shrink_slab() case. If the semaphore is contended, the caller will still check cond_resched(). After each successful call into a shrinker, the check for cond_resched() is still necessary in case one shrinker call is particularly slow. This patch replaces mm-vmscan-if-kswapd-has-been-running-too-long-allow-it-to-sleep.patch in -mm. [mgorman@suse.de: Preserve call to cond_resched after each call into shrinker] From: Minchan Kim Signed-off-by: Mel Gorman --- mm/vmscan.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index af24d1e..0bed248 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -230,8 +230,11 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, if (scanned == 0) scanned = SWAP_CLUSTER_MAX; - if (!down_read_trylock(&shrinker_rwsem)) - return 1; /* Assume we'll be able to shrink next time */ + if (!down_read_trylock(&shrinker_rwsem)) { + /* Assume we'll be able to shrink next time */ + ret = 1; + goto out; + } list_for_each_entry(shrinker, &shrinker_list, list) { unsigned long long delta; @@ -282,6 +285,8 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, shrinker->nr += total_scan; } up_read(&shrinker_rwsem); +out: + cond_resched(); return ret; } -- 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/