From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 22 May 2007 22:31:16 +0200 From: Ingo Molnar Subject: Re: [ck] Re: [PATCH] mm: swap prefetch improvements Message-ID: <20070522203116.GA8656@elte.hu> References: <20070430162007.ad46e153.akpm@linux-foundation.org> <200705222020.58474.kernel@kolivas.org> <20070522102530.GB2344@elte.hu> <200705222037.54741.kernel@kolivas.org> <20070522104648.GA10622@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Michael Chang Cc: Con Kolivas , Nick Piggin , Ray Lee , linux-kernel@vger.kernel.org, ck list , linux-mm@kvack.org, Andrew Morton List-ID: * Michael Chang wrote: > > It clearly should not consider 'itself' as IO activity. This > > suggests some bug in the 'detect activity' mechanism, agreed? I'm > > wondering whether you are seeing the same problem, or is all > > swap-prefetch IO on your system continuous until it's done [or some > > other IO comes inbetween]? > > The only "problem" I can see with this idea is in the potential case > that it takes up all the IO activity, and so there is never enough IO > activity from other progams to trigger the wait mechanism because they > don't get a chance to run. i dont understand what you mean. Any 'use only idle IO capacity' mechanism should immediately cease to be active the moment any other app tries to do IO - whether the IO subsystem is saturated or not. > That said, I don't think there are any issues with the code > compensating for its own activity in the "detect activity" mechanism > -- assuming there wasn't a major impact in e.g. maintainability or > something. > > As for the burstyness... considering the "no negative impact" stance, > I can understand that. But it seems inefficient, at best... well, it's a plain old bug (a not too serious one) in my book, i'm surprised that we are now at mail #7 about it :-) I reported it, and i guess Con will fix it eventually. There's really no need to deny that it exists or to try to talk it out of existence. Sheesh! :-) Ingo -- 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