From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 73AD56B008C for ; Tue, 23 Nov 2010 09:59:14 -0500 (EST) Date: Tue, 23 Nov 2010 14:58:56 +0000 From: Mel Gorman Subject: Re: [RFC 1/2] deactive invalidated pages Message-ID: <20101123145856.GQ19571@csn.ul.ie> References: <20101122141449.9de58a2c.akpm@linux-foundation.org> <20101122210132.be9962c7.akpm@linux-foundation.org> <20101123093859.GE19571@csn.ul.ie> <87k4k49jii.fsf@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <87k4k49jii.fsf@gmail.com> Sender: owner-linux-mm@kvack.org To: Ben Gamari Cc: Andrew Morton , Minchan Kim , linux-mm , LKML , Peter Zijlstra , Rik van Riel , KOSAKI Motohiro , Johannes Weiner , Nick Piggin List-ID: On Tue, Nov 23, 2010 at 09:55:49AM -0500, Ben Gamari wrote: > On Tue, 23 Nov 2010 09:38:59 +0000, Mel Gorman wrote: > > > If it's mapped pagecache then the user was being a bit silly (or didn't > > > know that some other process had mapped the file). In which case we > > > need to decide what to do - leave the page alone, deactivate it, or > > > half-deactivate it as this patch does. > > > > > > > What are the odds of an fadvise() user having used mincore() in advance > > to determine if the page was in use by another process? I would guess > > "low" so this half-deactivate gives a chance for the page to be promoted > > again as well as a chance for the flusher threads to clean the page if > > it really is to be reclaimed. > > > Do we really want to make the user jump through such hoops as using > mincore() just to get the kernel to handle use-once pages properly? I would think "no" which is why I support half-deactivating pages so they won't have to. The downside is that it's essentially a race window as another process needs to reactivate the page before it gets reclaimed to avoid a major fault. > I hope the answer is no. I know that fadvise isn't supposed to be a > magic bullet, but it would be nice if more processes would use it to > indicate their access patterns and the only way that will happen is if > it is reasonably straightforward to use. > > - Ben > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org