From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030253AbWI1RKQ (ORCPT ); Thu, 28 Sep 2006 13:10:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751955AbWI1RKQ (ORCPT ); Thu, 28 Sep 2006 13:10:16 -0400 Received: from excu-mxob-2.symantec.com ([198.6.49.23]:62092 "EHLO excu-mxob-2.symantec.com") by vger.kernel.org with ESMTP id S1751954AbWI1RKN (ORCPT ); Thu, 28 Sep 2006 13:10:13 -0400 Date: Thu, 28 Sep 2006 18:09:33 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.wat.veritas.com To: Neil Brown cc: "J. Bruce Fields" , Andrew Morton , nfs@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [NFS] [PATCH 009 of 11] knfsd: Allow max size of NFSd payload to be configured. In-Reply-To: <17691.19982.162616.572205@cse.unsw.edu.au> Message-ID: References: <20060824162917.3600.patches@notabene> <1060824063716.5020@suse.de> <20060925212457.GK32762@fieldses.org> <17691.19982.162616.572205@cse.unsw.edu.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-OriginalArrivalTime: 28 Sep 2006 17:09:25.0839 (UTC) FILETIME=[D9C0D5F0:01C6E320] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 28 Sep 2006, Neil Brown wrote: > But are the pages that totalram is measure in, normal pages, of > page_cache pages? And is there a difference? There's never yet been a difference, outside of some patches by bcrl. But totalram_pages comes "before" any idea of page cache, so it's in normal pages. > Should we use PAGE_CACHE_SHIFT, or PAGE_SHIFT? PAGE_SHIFT. > And why do we have both if they are numerically identical? Very irritating: the time I've wasted on "correcting" code for the "difference" between them! Yet there's still plenty wrong and I've largely given up on it. Probably never will be a difference: but the idea was that the page cache might use >0-order pages (unclear what happens to swap cache). I wish they'd waited for a working implementation before introducing the distinction; but never quite felt like deleting all trace of it. > > I'll submit a patch which uses > 12 - PAGE_SHIFT > in a little while. I haven't seen your context; but "12 - PAGE_SHIFT" sounds like a bad idea on all those architectures with PAGE_SHIFT 13 or more; you'll be on much safer ground working with "PAGE_SHIFT - 12". Hugh