From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 19 Sep 2007 12:11:26 +0100 Subject: Re: [PATCH/RFC 6/14] Reclaim Scalability: "No Reclaim LRU Infrastructure" Message-ID: <20070919111125.GD14817@skynet.ie> References: <20070914205359.6536.98017.sendpatchset@localhost> <20070914205438.6536.49500.sendpatchset@localhost> <1190042245.5460.81.camel@localhost> <20070918095443.GA2035@skynet.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: From: mel@skynet.ie (Mel Gorman) Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Lee Schermerhorn , linux-mm@kvack.org, akpm@linux-foundation.org, riel@redhat.com, balbir@linux.vnet.ibm.com, andrea@suse.de, a.p.zijlstra@chello.nl, eric.whitney@hp.com, npiggin@suse.de List-ID: On (18/09/07 12:45), Christoph Lameter didst pronounce: > On Tue, 18 Sep 2007, Mel Gorman wrote: > > > > Also the ramfs/shmem pages. There > > > may be uses though that require a page to stay put because it is used for > > > some nefarious I/O purpose by a driver. RDMA comes to mind. > > > > Yeah :/ > > > > > Maybe we need > > > some additional option that works like MLOCK but forbids migration. > > > > The problem with RDMA that I recall is that we don't know at allocation > > time that they may be unmovable sometimes in the future. I didn't think > > of a way around that problem. > > The current way that we have around the problem is to increase the page > count. With that all attempts to unmap the page by migration or otherwise > fail and the page stays put. > > RDMA is probably only temporarily pinning these while I/O is in progress?. > Our applications (XPMEM) > may pins them for good. > I'm not that familiar with XPMEM. What is it doing that can pin memory permanently? > > > Those > > > would then be unreclaimable and not __GFP_MOVABLE. I know some of our > > > applications create huge amount of these. > > > > > > > Can you think of a way that pages that will be later pinned by something > > like RDMA can be identified in advance? > > No. Nor in our XPMEM situation. We could move them at the point when they > are pinned to another section? > XPMEM could do that all right. Allocate a non-movable page, copy and pin. -- 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/ . Don't email: email@kvack.org