From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 00/28] Swap over NFS -v16 Date: Tue, 26 Feb 2008 16:43:49 +0100 Message-ID: <1204040629.6242.326.camel@lappy> References: <20080220144610.548202000@chello.nl> <20080223000620.7fee8ff8.akpm@linux-foundation.org> <18371.43950.150842.429997@notabene.brown> <1204023042.6242.271.camel@lappy> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: neilb@suse.de, akpm@linux-foundation.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, trond.myklebust@fys.uio.no To: Miklos Szeredi Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:51408 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763079AbYBZPoL (ORCPT ); Tue, 26 Feb 2008 10:44:11 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2008-02-26 at 16:29 +0100, Miklos Szeredi wrote: > > > mm-page_file_methods.patch > > > > > > This makes page_offset and others more expensive by adding a > > > conditional jump to a function call that is not usually made. > > > > > > Why do swap pages have a different index to everyone else? > > > > Because the page->index of an anonymous page is related to its (anon)vma > > so that it satisfies the constraints for vm_normal_page(). > > > > The index in the swap file it totally unrelated and quite random. Hence > > the swap-cache uses page->private to store it in. > > Yeah, and putting the condition into page_offset() will confuse code > which uses it for finding the offset in the VMA or in a tmpfs file. > > So why not just have a separate page_swap_offset() function, used > exclusively by swap_in/out()? Ah, we can do the page_file_offset() to match page_file_index() and page_file_mapping(). And convert NFS to use page_file_offset() where appropriate, as I already did for these others. That would sort out the mess, right?