From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [patch] rewrite rd Date: Tue, 4 Dec 2007 11:10:09 +0100 Message-ID: <20071204101009.GB9618@wotan.suse.de> References: <20071204042628.GA26636@wotan.suse.de> <200712041054.51599.borntraeger@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Linux Kernel Mailing List , linux-fsdevel@vger.kernel.org, "Eric W. Biederman" , Andrew Morton , rob@landley.net, Jens Axboe To: Christian Borntraeger Return-path: Received: from ns2.suse.de ([195.135.220.15]:51423 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752177AbXLDKKL (ORCPT ); Tue, 4 Dec 2007 05:10:11 -0500 Content-Disposition: inline In-Reply-To: <200712041054.51599.borntraeger@de.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Dec 04, 2007 at 10:54:51AM +0100, Christian Borntraeger wrote: > Am Dienstag, 4. Dezember 2007 schrieb Nick Piggin: > [...] > > There is one slight downside -- direct block device access and filesystem > > metadata access goes through an extra copy and gets stored in RAM twice. > > However, this downside is only slight, because the real buffercache of the > > device is now reclaimable (because we're not playing crazy games with it), > > so under memory intensive situations, footprint should effectively be the > > same -- maybe even a slight advantage to the new driver because it can also > > reclaim buffer heads. > > This is just an idea, I dont know if it is worth the trouble, but have you > though about implementing direct_access for brd? That would allow > execute-in-place (xip) on brd eliminating the extra copy. Actually that's a pretty good idea. It would allow xip to be tested without special hardware as well... I'll see what the patch looks like. Thanks