From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lazybastard.de ([212.112.238.170] helo=longford.logfs.org) by bombadil.infradead.org with esmtps (Exim 4.68 #1 (Red Hat Linux)) id 1JkGhN-0006ek-Vp for linux-mtd@lists.infradead.org; Fri, 11 Apr 2008 10:41:38 +0000 Date: Fri, 11 Apr 2008 12:41:28 +0200 From: =?utf-8?B?SsO2cm4=?= Engel To: Arnd Bergmann Subject: Re: [patch 4/15] fs/logfs/compr.c Message-ID: <20080411104128.GG25462@logfs.org> References: <20080401181308.512473173@logfs.org> <20080401181332.853833004@logfs.org> <200804101613.48465.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <200804101613.48465.arnd@arndb.de> Cc: linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 10 April 2008 16:13:47 +0200, Arnd Bergmann wrote: > > How much time is spent in the compression code? Would it be helpful > to have a percpu stream and do preempt_disable around it instead > of the mutex? > > That would improve parallelism and cache-locality of the compression, > at the cost of adding a source of latency to preemptible kernels. Several years back (before logfs) I was planning to do just that. It turned out that ipsec doesn't work in such a fashion, because each connection is a stream. And the two block-oriented users, jffs2 and cramfs just weren't worth it. Might be a good idea by now. I guess it should become self-contained code, so that jffs2, cramfs and ubifs can use it as well. Jörn -- Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface. -- Doug MacIlroy From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760221AbYDKKlq (ORCPT ); Fri, 11 Apr 2008 06:41:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758944AbYDKKlh (ORCPT ); Fri, 11 Apr 2008 06:41:37 -0400 Received: from lazybastard.de ([212.112.238.170]:57019 "EHLO longford.logfs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758688AbYDKKlg (ORCPT ); Fri, 11 Apr 2008 06:41:36 -0400 Date: Fri, 11 Apr 2008 12:41:28 +0200 From: =?utf-8?B?SsO2cm4=?= Engel To: Arnd Bergmann Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org Subject: Re: [patch 4/15] fs/logfs/compr.c Message-ID: <20080411104128.GG25462@logfs.org> References: <20080401181308.512473173@logfs.org> <20080401181332.853833004@logfs.org> <200804101613.48465.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <200804101613.48465.arnd@arndb.de> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 10 April 2008 16:13:47 +0200, Arnd Bergmann wrote: > > How much time is spent in the compression code? Would it be helpful > to have a percpu stream and do preempt_disable around it instead > of the mutex? > > That would improve parallelism and cache-locality of the compression, > at the cost of adding a source of latency to preemptible kernels. Several years back (before logfs) I was planning to do just that. It turned out that ipsec doesn't work in such a fashion, because each connection is a stream. And the two block-oriented users, jffs2 and cramfs just weren't worth it. Might be a good idea by now. I guess it should become self-contained code, so that jffs2, cramfs and ubifs can use it as well. Jörn -- Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface. -- Doug MacIlroy