From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from www.linux.org.uk (parcelfarce.linux.theplanet.co.uk [195.92.249.252]) by dsl2.external.hp.com (Postfix) with ESMTP id 6E639482B for ; Sat, 8 Mar 2003 16:27:37 -0700 (MST) Received: from willy by www.linux.org.uk with local (Exim 3.33 #5) id 18rnj6-0005WT-00; Sat, 08 Mar 2003 23:27:36 +0000 Date: Sat, 8 Mar 2003 23:27:36 +0000 From: Matthew Wilcox To: "David S. Miller" Cc: willy@debian.org, grundler@dsl2.external.hp.com, jsm@udlkern.fc.hp.com, parisc-linux@lists.parisc-linux.org Subject: Re: [parisc-linux] Re: RFC: mmap patch Message-ID: <20030308232736.N3865@parcelfarce.linux.theplanet.co.uk> References: <20030308172439.GA10161@dsl2.external.hp.com> <20030308.110459.35972945.davem@redhat.com> <20030308224503.L3865@parcelfarce.linux.theplanet.co.uk> <20030308.150023.97153009.davem@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20030308.150023.97153009.davem@redhat.com>; from davem@redhat.com on Sat, Mar 08, 2003 at 03:00:23PM -0800 Sender: parisc-linux-admin@lists.parisc-linux.org Errors-To: parisc-linux-admin@lists.parisc-linux.org List-Help: List-Post: List-Subscribe: , List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: On Sat, Mar 08, 2003 at 03:00:23PM -0800, David S. Miller wrote: > You need merely 8MB of address space (2 * 4MB) if you implement > my {copy,clear}_user_page() dynamic mapping hack, that will be > tons more cheaper than any kmap based scheme and also be nicer > on the TLB as there will be zero TLB changes occurring around > the copy/clear. > > People can continue to talk about all their bright new idea, which > is fine, but it feels like my known-working ideas are being ignored. Sorry, I think you've misunderstood the problem. This is write() vs mmap(). We call flush_dcache_page() after the write() -- but PA's flush_dcache_page() only flushes the kernel's mapping of that page, not the user's. The question is how to fix that. Randolph published a patch which flushes two pages -- one which is the kernel's view of the page, and one which is the user's view of the page. John disagreed that was necessary, and I'm proposing a way (with kmap) to avoid it. Nothing to do with copy/clear_user_page(). -- "It's not Hollywood. War is real, war is primarily not about defeat or victory, it is about death. I've seen thousands and thousands of dead bodies. Do you think I want to have an academic debate on this subject?" -- Robert Fisk