From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 2 Mar 2007 10:23:15 -0800 From: Andrew Morton Subject: Re: The performance and behaviour of the anti-fragmentation related patches Message-Id: <20070302102315.e0728a42.akpm@linux-foundation.org> In-Reply-To: References: <20070301101249.GA29351@skynet.ie> <20070301160915.6da876c5.akpm@linux-foundation.org> <45E842F6.5010105@redhat.com> <20070302085838.bcf9099e.akpm@linux-foundation.org> <20070302093501.34c6ef2a.akpm@linux-foundation.org> <45E8624E.2080001@redhat.com> <20070302100619.cec06d6a.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Rik van Riel , Mel Gorman , npiggin@suse.de, mingo@elte.hu, jschopp@austin.ibm.com, arjan@infradead.org, torvalds@linux-foundation.org, mbligh@mbligh.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Fri, 2 Mar 2007 10:15:36 -0800 (PST) Christoph Lameter wrote: > On Fri, 2 Mar 2007, Andrew Morton wrote: > > > > One particular case is a 32GB system with a database that takes most > > > of memory. The amount of actually freeable page cache memory is in > > > the hundreds of MB. > > > > Where's the rest of the memory? tmpfs? mlocked? hugetlb? > > The memory is likely in use but there is enough memory free in unmapped > clean pagecache pages so that we occasionally are able to free pages. Then > the app is reading more from disk replenishing that ... > Thus we are forever cycling through the LRU lists moving pages between > the lists aging etc etc. Can lead to a livelock. Guys, with this level of detail thses problems will never be fixed. > > > A third scenario is where a system has way more RAM than swap, and not > > > a whole lot of freeable page cache. In this case, the VM ends up > > > spending WAY too much CPU time scanning and shuffling around essentially > > > unswappable anonymous memory and tmpfs files. > > > > Well we've allegedly fixed that, but it isn't going anywhere without > > testing. > > We have fixed the case in which we compile the kernel without swap. Then > anonymous pages behave like mlocked pages. Did we do more than that? oh yeah, we took the ran-out-of-swapcache code out. But if we're going to do this thing, we should find some way to bring it back. -- 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