From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 7 Mar 2007 01:26:38 -0800 From: Andrew Morton Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Message-Id: <20070307012638.793d9a9f.akpm@linux-foundation.org> In-Reply-To: <20070307091823.GA8609@wotan.suse.de> References: <20070221023656.6306.246.sendpatchset@linux.site> <20070221023735.6306.83373.sendpatchset@linux.site> <20070306225101.f393632c.akpm@linux-foundation.org> <20070307070853.GB15877@wotan.suse.de> <20070307081948.GA9563@wotan.suse.de> <20070307082755.GA25733@elte.hu> <20070307004709.432ddf97.akpm@linux-foundation.org> <20070307010756.b31c8190.akpm@linux-foundation.org> <20070307091823.GA8609@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Miklos Szeredi , mingo@elte.hu, linux-mm@kvack.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, Peter Zijlstra List-ID: On Wed, 7 Mar 2007 10:18:23 +0100 Nick Piggin wrote: > On Wed, Mar 07, 2007 at 01:07:56AM -0800, Andrew Morton wrote: > > On Wed, 07 Mar 2007 09:51:57 +0100 Miklos Szeredi wrote: > > > > > > > Dirty page accounting doesn't work either on > > > > > non-linear mappings > > > > > > > > It doesn't? Confused - these things don't have anything to do with each > > > > other do they? > > > > > > Look in page_mkclean(). Where does it handle non-linear mappings? > > > > > > > OK, I'd forgotten about that. It won't break dirty memory accounting, > > but it'll potentially break dirty memory balancing. > > > > If we have the wrong page (due to nonlinear), page_check_address() will > > fail and we'll leave the pte dirty. That puts us back to the pre-2.6.17 > > algorithms and I guess it'll break the msync guarantees. > > > > Peter, I thought we went through the nonlinear problem ages ago and decided > > it was OK? > > msync breakage is bad, but otherwise I don't know that we care about > dirty page writeout efficiency. Well. We made so many changes to support the synchronous dirty-the-page-when-we-dirty-the-pte thing that I'm rather doubtful that the old-style approach still works. It might seem to, most of the time. But if it _is_ subtly broken, boy it's going to take a long time for us to find out. > But I think we discovered that those msync changes are bogus anyway > becuase there is a small race window where pte could be dirtied without > page being set dirty? Dunno, I don't recall that. We dirty the page before the pte... -- 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