From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753003Ab1EWJyN (ORCPT ); Mon, 23 May 2011 05:54:13 -0400 Received: from cantor2.suse.de ([195.135.220.15]:54798 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751204Ab1EWJyC (ORCPT ); Mon, 23 May 2011 05:54:02 -0400 From: Mel Gorman To: Andrew Morton Cc: James Bottomley , Colin King , Raghavendra D Prabhu , Jan Kara , Chris Mason , Christoph Lameter , Pekka Enberg , Rik van Riel , Johannes Weiner , Minchan Kim , linux-fsdevel , linux-mm , linux-kernel , linux-ext4 , stable , Mel Gorman Subject: [PATCH 2/2] mm: vmscan: Correctly check if reclaimer should schedule during shrink_slab Date: Mon, 23 May 2011 10:53:55 +0100 Message-Id: <1306144435-2516-3-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.7.3.4 In-Reply-To: <1306144435-2516-1-git-send-email-mgorman@suse.de> References: <1306144435-2516-1-git-send-email-mgorman@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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() remains in case one shrinker 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 1aa262b..cc1470b 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; } -- 1.7.3.4 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Subject: [PATCH 2/2] mm: vmscan: Correctly check if reclaimer should schedule during shrink_slab Date: Mon, 23 May 2011 10:53:55 +0100 Message-ID: <1306144435-2516-3-git-send-email-mgorman@suse.de> References: <1306144435-2516-1-git-send-email-mgorman@suse.de> Cc: James Bottomley , Colin King , Raghavendra D Prabhu , Jan Kara , Chris Mason , Christoph Lameter , Pekka Enberg , Rik van Riel , Johannes Weiner , Minchan Kim , linux-fsdevel , linux-mm , linux-kernel , linux-ext4 , stable , Mel Gorman To: Andrew Morton Return-path: In-Reply-To: <1306144435-2516-1-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org 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() remains in case one shrinker 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 1aa262b..cc1470b 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; } -- 1.7.3.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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