From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 8 Nov 2007 10:56:59 -0800 From: Andrew Morton Subject: Re: bug #5493 Message-Id: <20071108105659.3ca01b00.akpm@linux-foundation.org> In-Reply-To: <20071108131518.5408931d@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> 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 13:15:18 -0500 Rik van Riel wrote: > On Thu, 8 Nov 2007 09:57:04 -0800 > Andrew Morton wrote: > > > > On Thu, 8 Nov 2007 16:53:20 +0000 mel@skynet.ie (Mel Gorman) wrote: > > > On (07/11/07 19:12), Andrew Morton didst pronounce: > > > > (added linux-mm) > > > > > > > > > On Wed, 7 Nov 2007 18:00:20 -0800 "Natalie Protasevich" wrote: > > > > > Andrew, this one http://bugzilla.kernel.org/show_bug.cgi?id=5493 looks > > > > > serious, and I'm not sure who to ping now that the reporter can't test > > > > > it anymore. > > > > > This is about mprotect ... > > > > > > > > No, I don't think anyone knows how to fix that. > > > > > > > > Fortunately I'm only aware of the one person hitting this problem. > > > > > > > > > > I tried out the test program with 1GiB of memory. First, the program could > > > not even run unless mprotect was called again to make pages read-only a > > > second time - otherwise mprotect would report ENOMEM because VMAs were not > > > getting merged. That in itself was a little unexpected. > > > > > > After fixing that, I ran with varying number of pages and got the > > > following timings > > > > > > 300000: 68.36 seconds > > > 295000: 55.07 seconds > > > 290000: 41.79 seconds > > > 285000: 31.71 seconds > > > 280000: 22.92 seconds > > > 275000: 11.27 seconds > > > 270000: 5.60 seconds > > > 265000: 5.94 seconds > > > 260000: 5.77 seconds > > > 255000: 5.65 seconds > > > 250000: 5.53 seconds > > > 245000: 5.42 seconds > > > 240000: 5.31 seconds > > > > > > The system has about 250000 pages and around that mark it seemed fine in > > > terms of time-to-completion. Above that vmstat was showing high figures > > > for si/so which is not a major suprise as such. > > > > hm, I was able to reproduce it way back when it was first reported. See > > below. > > > > > > > If this only occurs on systems with large amounts of memory, could it be > > > a variation of the excessive page-scanning problem that Rik has been on > > > about? > > > > 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. -- 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