From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 15 Mar 2007 15:06:01 -0700 From: Andrew Morton Subject: Re: [PATCH] mm/filemap.c: unconditionally call mark_page_accessed Message-Id: <20070315150601.682036cf.akpm@linux-foundation.org> In-Reply-To: <20070315214923.GE6687@v2.random> References: <20070312173500.GF23532@duck.suse.cz> <20070313185554.GA5105@duck.suse.cz> <1173905741.8763.36.camel@kleikamp.austin.ibm.com> <20070314213317.GA22234@rhlx01.hs-esslingen.de> <1173910138.8763.45.camel@kleikamp.austin.ibm.com> <45F8A301.90301@cse.ohio-state.edu> <20070315110735.287c8a23.akpm@linux-foundation.org> <20070315214923.GE6687@v2.random> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrea Arcangeli Cc: Ashif Harji , dingxn@cse.ohio-state.edu, shaggy@linux.vnet.ibm.com, andi@rhlx01.fht-esslingen.de, linux-mm@kvack.org, npiggin@suse.de, jack@suse.cz, linux-kernel@vger.kernel.org List-ID: On Thu, 15 Mar 2007 22:49:23 +0100 Andrea Arcangeli wrote: > On Thu, Mar 15, 2007 at 11:07:35AM -0800, Andrew Morton wrote: > > > On Thu, 15 Mar 2007 01:22:45 -0400 (EDT) Ashif Harji wrote: > > > I still think the simple fix of removing the > > > condition is the best approach, but I'm certainly open to alternatives. > > > > Yes, the problem of falsely activating pages when the file is read in small > > hunks is worse than the problem which your patch fixes. > > Really? I would have expected all performance sensitive apps to read > in >=PAGE_SIZE chunks. And if they don't because they split their > dataset in blocks (like some database), it may not be so wrong to > activate those pages that have two "hot" blocks more aggressively than > those pages with a single hot block. But the problem which is being fixed here is really obscure: an application repeatedly reading the first page and only the first page of a file, always via the same fd. I'd expect that the sub-page-size read scenarion happens heaps more often than that, especially when dealing with larger PAGE_SIZEs. -- 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