From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 8 Nov 2007 20:27:07 -0800 From: Andrew Morton Subject: Re: bug #5493 Message-Id: <20071108202707.d7efed57.akpm@linux-foundation.org> In-Reply-To: <20071108200041.1a739bc5@bree.surriel.com> References: <32209efe0711071800v4bc0c62er7bc462f1891c9dcd@mail.gmail.com> <20071107191247.04d74241.akpm@linux-foundation.org> <20071108165320.GA23882@skynet.ie> <20071108095704.f98905ec.akpm@linux-foundation.org> <20071108131518.5408931d@bree.surriel.com> <20071108105659.3ca01b00.akpm@linux-foundation.org> <20071108200041.1a739bc5@bree.surriel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: mel@skynet.ie, protasnb@gmail.com, linux-mm@kvack.org List-ID: > On Thu, 8 Nov 2007 20:00:41 -0500 Rik van Riel wrote: > On Thu, 8 Nov 2007 10:56:59 -0800 > Andrew Morton wrote: > > > On Thu, 8 Nov 2007 13:15:18 -0500 Rik van Riel wrote: > > > On Thu, 8 Nov 2007 09:57:04 -0800 > > > > > No, it was due to linear traversal of very long reverse-mapping lists > > > > (thousands of elements, irrc). > > > > > > Traversal at pageout time, or at mprotect time? > > > > > > > pageout, iirc. For each page we were walking a linear list of I think > > ~10,000 elements. > > Pageout scan complexity in this workload is O(P*M), where > P is the number of pages scanned and M is the number of > mappings. > > My code will, in the next iteration, reduce P by a fair > amount for larger amounts of memory, but M is still very > large... That's yet to be proven - for the vast majority of workloads your P is already very small. > I might use this test case to play with the SEQ replacement > of anonymous pages. Figuring out how to avoid some worst > case that people really hit in practice is often educational. I don't think we can anywhere near fix this without basic redesign of VM data structures and the relationship between them. -- 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