From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 2F2326B01F0 for ; Wed, 24 Mar 2010 15:55:13 -0400 (EDT) Date: Wed, 24 Mar 2010 14:54:32 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH 11/11] Do not compact within a preferred zone after a compaction failure In-Reply-To: <20100324103749.GB21147@csn.ul.ie> Message-ID: References: <1269347146-7461-1-git-send-email-mel@csn.ul.ie> <1269347146-7461-12-git-send-email-mel@csn.ul.ie> <20100323183936.GF5870@csn.ul.ie> <20100324103749.GB21147@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , Andrea Arcangeli , Adam Litke , Avi Kivity , David Rientjes , Minchan Kim , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Wed, 24 Mar 2010, Mel Gorman wrote: > > > What I was thinking at the time was that compact_resume was stored in struct > > > zone - i.e. that is where it is recorded. > > > > Ok adding a dozen or more words here may be useful. > > > > In the event of compaction followed by an allocation failure, this patch > defers further compaction in the zone for a period of time. The zone that > is deferred is the first zone in the zonelist - i.e. the preferred zone. > To defer compaction in the other zones, the information would need to > be stored in the zonelist or implemented similar to the zonelist_cache. > This would impact the fast-paths and is not justified at this time. > > ? Ok. > > There are frequent uses of HZ/10 as well especially in vmscna.c. A longer > > time may be better? HZ/50 looks like an interval for writeout. But this > > is related to reclaim? > > > > HZ/10 is somewhat of an arbitrary choice as well and there isn't data on > which is better and which is worse. If the zone is full of dirty data, then > HZ/10 makes sense for IO. If it happened to be mainly clean cache but under > heavy memory pressure, then reclaim would be a relatively fast event and a > shorter wait makes sense of HZ/50. > > Thing is, if we start with a short timer and it's too short, COMPACTFAIL > will be growing steadily. If we choose a long time and it's too long, there > is no counter to indicate it was a bad choice. Hence, I'd prefer the short > timer to start with and ideally resume compaction after some event in the > future rather than depending on time. > > Does that make sense? Yes. -- 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/ . Don't email: email@kvack.org