From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 16 Mar 2007 00:28:37 +0100 From: Andrea Arcangeli Subject: Re: [PATCH] mm/filemap.c: unconditionally call mark_page_accessed Message-ID: <20070315232837.GH6687@v2.random> References: <20070312173500.GF23532@duck.suse.cz> <20070313185554.GA5105@duck.suse.cz> <45F96CCB.4000709@redhat.com> <20070315162944.GI8321@wotan.suse.de> <20070315225928.GF6687@v2.random> <1174000545.14380.22.camel@kleikamp.austin.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1174000545.14380.22.camel@kleikamp.austin.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Dave Kleikamp Cc: Hugh Dickins , Nick Piggin , Chuck Ebbert , Ashif Harji , Miquel van Smoorenburg , linux-mm@kvack.org, Jan Kara , linux-kernel@vger.kernel.org, akpm@linux-foundation.org List-ID: On Thu, Mar 15, 2007 at 06:15:45PM -0500, Dave Kleikamp wrote: > On Thu, 2007-03-15 at 23:59 +0100, Andrea Arcangeli wrote: > > On Thu, Mar 15, 2007 at 05:44:01PM +0000, Hugh Dickins wrote: > > > who removed the !offset condition, he should be consulted on its > > > reintroduction. > > > > the !offset check looks a pretty broken heuristic indeed, it would > > break random I/O. > > I wouldn't call it broken. At worst, I'd say it's imperfect. But > that's the nature of a heuristic. It most likely works in a huge > majority of cases. well, IMHO in the huge majority of cases the prev_page check isn't necessary in the first place (and IMHO it hurts a lot more than it can help, as demonstrated by specweb, since we'll bite on the good guys to help the bad guys). The only case where I can imagine the prev_page to make sense is to handle contiguous I/O made with a small buffer, so clearly an inefficient code in the first place. But if this guy is reading with email@kvack.org