From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 5 Dec 2006 21:47:21 +0000 Subject: Re: [PATCH] Add __GFP_MOVABLE for callers to flag allocations that may be migrated Message-ID: <20061205214721.GE20614@skynet.ie> References: <20061204113051.4e90b249.akpm@osdl.org> <20061204120611.4306024e.akpm@osdl.org> <20061204131959.bdeeee41.akpm@osdl.org> <20061204142259.3cdda664.akpm@osdl.org> <20061205112541.2a4b7414.akpm@osdl.org> 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: Andrew Morton , Linux Memory Management List , Linux Kernel Mailing List List-ID: On (05/12/06 12:01), Christoph Lameter didst pronounce: > On Tue, 5 Dec 2006, Andrew Morton wrote: > > > > We always run reclaim against the whole zone not against parts. Why > > > would we start running reclaim against a portion of a zone? > > > > Oh for gawd's sake. > > Yes indeed. Another failure to answer a simple question. > There are times you want to reclaim just part of a zone - specifically satisfying a high-order allocations. See sitations 1 and 2 from elsewhere in this thread. On a similar vein, there will be times when you want to migrate a PFN range for similar reasons. > > If you want to allocate a page from within the first 1/4 of a zone, and if > > all those pages are in use for something else then you'll need to run > > reclaim against the first 1/4 of that zone. Or fail the allocation. Or > > run reclaim against the entire zone. The second two options are > > self-evidently dumb. > > Why would one want to allocate from the 1/4th of a zone? (Are we still > discussing Mel's antifrag scheme or what is this about?) > Because you wanted contiguous blocks of pages. This is related to anti-frag because with anti-frag, reclaiming memory or migration memory will free up contiguous blocks. Without it, you're probably wasting your time. -- 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