From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 5 Jun 2002 16:19:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 5 Jun 2002 16:19:56 -0400 Received: from [195.39.17.254] ([195.39.17.254]:13984 "EHLO Elf.ucw.cz") by vger.kernel.org with ESMTP id ; Wed, 5 Jun 2002 16:19:17 -0400 Date: Wed, 5 Jun 2002 13:22:55 +0200 From: Pavel Machek To: Hugh Dickins Cc: Linus Torvalds , Andrea Arcangeli , Andrew Morton , lkml Subject: Re: [patch 5/18] mark swapout pages PageWriteback() Message-ID: <20020605112254.GA1567@elf.ucw.cz> In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.28i X-Warning: Reading this can be dangerous to your mental health. Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > In short the same way MAP_ANON must pageout correctly, also MAP_SHARED > > > must swapout correctly with very vm intensive conditions. > > I strongly agree with Andrea on that. Swap fault without page lock > was a step forward, reinstating it in the light of observed degradation > in one workload was right decision for that particular tail of release, > but it's a shame to have stayed that way. > > > That is true, but it is ignoring the fact that there _are_ real technical > > differences between swap cache mappings and regular shared mappings. > > > > One major difference is the approach to the last user: a last use of a > > shared mapping still needs to write out dirty state, while the last use of > > a swap page is better off noticing that it should just optimize away the > > write, and we can just turn the page back into a dirty anonymous page. > > Poor example: isn't last use of swap page just like last use of > shared mapping of an _unlinked_ file? Eh? Suppose I have two different shared mappings of (unlinked:3). It may be last use of swap page in first mapping, but what prevents me from seeking and trying to read what I wrote? Pavel -- (about SSSCA) "I don't say this lightly. However, I really think that the U.S. no longer is classifiable as a democracy, but rather as a plutocracy." --hpa