Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752447Ab1FYVeG (ORCPT ); Sat, 25 Jun 2011 17:34:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19503 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752190Ab1FYVeE (ORCPT ); Sat, 25 Jun 2011 17:34:04 -0400 Message-ID: <4E065433.3020502@redhat.com> Date: Sat, 25 Jun 2011 17:33:39 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Lightning/1.0b3pre Thunderbird/3.1.10 MIME-Version: 1.0 To: Mel Gorman CC: Andrew Morton , =?UTF-8?B?UMOhZHJhaWcgQnJh?= =?UTF-8?B?ZHk=?= , James Bottomley , Colin King , Minchan Kim , Andrew Lutomirski , Johannes Weiner , linux-mm , linux-kernel Subject: Re: [PATCH 1/4] mm: vmscan: Correct check for kswapd sleeping in sleeping_prematurely References: <1308926697-22475-1-git-send-email-mgorman@suse.de> <1308926697-22475-2-git-send-email-mgorman@suse.de> In-Reply-To: <1308926697-22475-2-git-send-email-mgorman@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1618 Lines: 37 On 06/24/2011 10:44 AM, Mel Gorman wrote: > During allocator-intensive workloads, kswapd will be woken frequently > causing free memory to oscillate between the high and min watermark. > This is expected behaviour. > > A problem occurs if the highest zone is small. balance_pgdat() > only considers unreclaimable zones when priority is DEF_PRIORITY > but sleeping_prematurely considers all zones. It's possible for this > sequence to occur > > 1. kswapd wakes up and enters balance_pgdat() > 2. At DEF_PRIORITY, marks highest zone unreclaimable > 3. At DEF_PRIORITY-1, ignores highest zone setting end_zone > 4. At DEF_PRIORITY-1, calls shrink_slab freeing memory from > highest zone, clearing all_unreclaimable. Highest zone > is still unbalanced > 5. kswapd returns and calls sleeping_prematurely > 6. sleeping_prematurely looks at *all* zones, not just the ones > being considered by balance_pgdat. The highest small zone > has all_unreclaimable cleared but but the zone is not > balanced. all_zones_ok is false so kswapd stays awake > > This patch corrects the behaviour of sleeping_prematurely to check > the zones balance_pgdat() checked. > > Reported-and-tested-by: Pádraig Brady > Signed-off-by: Mel Gorman Acked-by: Rik van Riel -- All rights reversed -- 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/