From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx136.postini.com [74.125.245.136]) by kanga.kvack.org (Postfix) with SMTP id 0C97F6B0031 for ; Mon, 3 Jun 2013 13:16:12 -0400 (EDT) Date: Mon, 3 Jun 2013 19:15:58 +0200 From: Peter Zijlstra Subject: Re: [patch 10/10] mm: workingset: keep shadow entries in check Message-ID: <20130603171558.GE8923@twins.programming.kicks-ass.net> References: <1369937046-27666-1-git-send-email-hannes@cmpxchg.org> <1369937046-27666-11-git-send-email-hannes@cmpxchg.org> <20130603082533.GH5910@twins.programming.kicks-ass.net> <20130603152032.GF15576@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130603152032.GF15576@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: linux-mm@kvack.org, Andi Kleen , Andrea Arcangeli , Andrew Morton , Greg Thelen , Christoph Hellwig , Hugh Dickins , Jan Kara , KOSAKI Motohiro , Mel Gorman , Minchan Kim , Rik van Riel , Michel Lespinasse , Seth Jennings , Roman Gushchin , metin d , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org On Mon, Jun 03, 2013 at 11:20:32AM -0400, Johannes Weiner wrote: > On Mon, Jun 03, 2013 at 10:25:33AM +0200, Peter Zijlstra wrote: > > On Thu, May 30, 2013 at 02:04:06PM -0400, Johannes Weiner wrote: > > > Previously, page cache radix tree nodes were freed after reclaim > > > emptied out their page pointers. But now reclaim stores shadow > > > entries in their place, which are only reclaimed when the inodes > > > themselves are reclaimed. This is problematic for bigger files that > > > are still in use after they have a significant amount of their cache > > > reclaimed, without any of those pages actually refaulting. The shadow > > > entries will just sit there and waste memory. In the worst case, the > > > shadow entries will accumulate until the machine runs out of memory. > > > > > > > Can't we simply prune all refault entries that have a distance larger > > than the memory size? Then we must assume that no refault entry means > > its too old, which I think is a fair assumption. > > Two workloads bound to two nodes might not push pages through the LRUs > at the same pace, so a distance might be bigger than memory due to the > faster moving node, yet still be a hit in the slower moving one. We > can't really know until we evaluate it on a per-zone basis. But wasn't patch 1 of this series about making sure each zone is scanned proportionally to its size? But given that, sure maybe 1 memory size is a bit strict, but surely we can put a limit on things at about 2 memory sizes? -- 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