Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753210Ab1F1XiP (ORCPT ); Tue, 28 Jun 2011 19:38:15 -0400 Received: from mail-qy0-f174.google.com ([209.85.216.174]:56715 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751668Ab1F1XiL convert rfc822-to-8bit (ORCPT ); Tue, 28 Jun 2011 19:38:11 -0400 MIME-Version: 1.0 In-Reply-To: <1308926697-22475-3-git-send-email-mgorman@suse.de> References: <1308926697-22475-1-git-send-email-mgorman@suse.de> <1308926697-22475-3-git-send-email-mgorman@suse.de> Date: Wed, 29 Jun 2011 08:38:10 +0900 Message-ID: Subject: Re: [PATCH 2/4] mm: vmscan: Do not apply pressure to slab if we are not applying pressure to zone From: Minchan Kim To: Mel Gorman Cc: Andrew Morton , =?UTF-8?Q?P=C3=A1draig_Brady?= , James Bottomley , Colin King , Andrew Lutomirski , Rik van Riel , Johannes Weiner , linux-mm , linux-kernel Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1394 Lines: 32 On Fri, Jun 24, 2011 at 11:44 PM, 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. > > When kswapd applies pressure to zones during node balancing, it checks > if the zone is above a high+balance_gap threshold. If it is, it does > not apply pressure but it unconditionally shrinks slab on a global > basis which is excessive. In the event kswapd is being kept awake due to > a high small unreclaimable zone, it skips zone shrinking but still > calls shrink_slab(). > > Once pressure has been applied, the check for zone being unreclaimable > is being made before the check is made if all_unreclaimable should be > set. This miss of unreclaimable can cause has_under_min_watermark_zone > to be set due to an unreclaimable zone preventing kswapd backing off > on congestion_wait(). > > Reported-and-tested-by: Pádraig Brady > Signed-off-by: Mel Gorman Reviewed-by: Minchan Kim It does make sense. -- Kind regards, Minchan Kim -- 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/