From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 1D6EB6B0110 for ; Tue, 28 Jun 2011 19:38:12 -0400 (EDT) Received: by qwa26 with SMTP id 26so516912qwa.14 for ; Tue, 28 Jun 2011 16:38:10 -0700 (PDT) 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: 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 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: P=C3=A1draig Brady > Signed-off-by: Mel Gorman Reviewed-by: Minchan Kim It does make sense. --=20 Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org