From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 28 Jul 2002 21:24:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 28 Jul 2002 21:24:27 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:6931 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Sun, 28 Jul 2002 21:24:26 -0400 Message-ID: <3D449C14.46683B2A@zip.com.au> Date: Sun, 28 Jul 2002 18:36:20 -0700 From: Andrew Morton X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.19-rc3-ac3 i686) X-Accept-Language: en MIME-Version: 1.0 To: William Lee Irwin III CC: Linux Kernel Subject: Re: [BK PATCH 2.5] Introduce 64-bit versions of PAGE_{CACHE_,}{MASK,ALIGN} References: <5.1.0.14.2.20020728193528.04336a80@pop.cus.cam.ac.uk> <3D448808.CF8D18BA@zip.com.au> <20020729005649.GT25038@holomorphy.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org William Lee Irwin III wrote: > > On Sun, Jul 28, 2002 at 05:10:48PM -0700, Andrew Morton wrote: > > - Few pages use ->private for much. Hash for it. 4(ish) bytes > > saved. > > Do you know an approximate reasonable constant of proportionality > for how many pages have ->private attached? Well, it depends on what the mapping is using ->private for. In the case of ext2, ext3 and (soon) reiserfs mappings, ->private is only used for pagecache pages which were written to with write(2). But for other filesystems, basically all pagecache pages have buffers at present, so I exaggerate. But as filesystems migrate to using direct-to-BIO reads, the situation gets better. It might be useful to buffer-strip written-to pages as well, if a clean way of doing that presents itself. Maybe in refill_inactive or something. > On Sun, Jul 28, 2002 at 05:10:48PM -0700, Andrew Morton wrote: > > - Remove the rmap chain (I just broke ptep_to_address() anyway). 4 bytes > > saved. struct page is now 20 bytes. > > How did ptep_to_address() break? I browsed over your latest changes and > missed the bit where that fell apart. I'll at least take a stab at fixing > it up until the other bits materialize. I broke it in my five-minute thought-coding exercise. By removing page->index. -