From patchwork Fri Jun 17 10:06:52 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Colin Ian King X-Patchwork-Id: 100791 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from chlorine.canonical.com (chlorine.canonical.com [91.189.94.204]) by ozlabs.org (Postfix) with ESMTP id A95CFB6FA3 for ; Fri, 17 Jun 2011 20:07:08 +1000 (EST) Received: from localhost ([127.0.0.1] helo=chlorine.canonical.com) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1QXVx5-0003sY-Kx; Fri, 17 Jun 2011 10:06:59 +0000 Received: from adelie.canonical.com ([91.189.90.139]) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1QXVx0-0003s9-Ji for kernel-team@lists.ubuntu.com; Fri, 17 Jun 2011 10:06:54 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by adelie.canonical.com with esmtp (Exim 4.71 #1 (Debian)) id 1QXVx0-00044q-Fe for ; Fri, 17 Jun 2011 10:06:54 +0000 Received: from cpc7-craw6-2-0-cust128.croy.cable.virginmedia.com ([94.172.219.129] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1QXVx0-0001iv-Bh for kernel-team@lists.ubuntu.com; Fri, 17 Jun 2011 10:06:54 +0000 From: Colin King To: kernel-team@lists.ubuntu.com Subject: [PATCH 1/2] mm: vmscan: correctly check if reclaimer should schedule during shrink_slab Date: Fri, 17 Jun 2011 11:06:52 +0100 Message-Id: <1308305213-4657-2-git-send-email-colin.king@canonical.com> X-Mailer: git-send-email 1.7.4.1 In-Reply-To: <1308305213-4657-1-git-send-email-colin.king@canonical.com> References: <1308305213-4657-1-git-send-email-colin.king@canonical.com> X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.13 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: kernel-team-bounces@lists.ubuntu.com Errors-To: kernel-team-bounces@lists.ubuntu.com From: Minchan Kim 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. [mgorman@suse.de: preserve call to cond_resched after each call into shrinker] Signed-off-by: Mel Gorman Signed-off-by: Minchan Kim Cc: Rik van Riel Cc: Johannes Weiner Cc: Wu Fengguang Cc: James Bottomley Tested-by: Colin King Cc: Raghavendra D Prabhu Cc: Jan Kara Cc: Chris Mason Cc: Christoph Lameter Cc: Pekka Enberg Cc: Rik van Riel Cc: [2.6.38+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Acked-by: Brad Figg Acked-by: Herton Ronaldo Krzesinski --- mm/vmscan.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 0665520..648aab8 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; }