From: Jan Kara Subject: Re: [RFC] Heads up on sys_fallocate() Date: Tue, 6 Mar 2007 15:50:09 +0100 Message-ID: <20070306145009.GB3661@duck.suse.cz> References: <20070225022326.137b4875.akpm@linux-foundation.org> <20070301183445.GA7911@amitarora.in.ibm.com> <20070301142537.b5950cd7.akpm@linux-foundation.org> <1172788855.26078.294.camel@edge> <20070301145256.3e999932.akpm@linux-foundation.org> <45E86CBA.3070905@us.ibm.com> <20070305122742.GA11486@atrey.karlin.mff.cuni.cz> <45EC7773.7020603@us.ibm.com> <20070306072850.GA23081@infradead.org> <45ED7C59.4050508@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Mingming Cao , Andrew Morton , nscott@aconex.com, "Amit K. Arora" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, suparna@in.ibm.com, alex@clusterfs.com, suzuki@in.ibm.com To: Ulrich Drepper Return-path: Content-Disposition: inline In-Reply-To: <45ED7C59.4050508@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Tue 06-03-07 06:36:09, Ulrich Drepper wrote: > Christoph Hellwig wrote: > > fallocate with the whence argument and flags is already quite complicated, > > I'd rather have another call for placement decisions, that would > > be called on an fd to do placement decissions for any further allocations > > (prealloc, write, etc) > > Yes, posix_fallocate shouldn't be made more complicated. But I don't > understand why requesting linear layout of the blocks should be an > option. It's always an advantage if the blocks requested this way are > linear on disk. So, the kernel should always do its best to make this > happen, without needing an additional option. Actually, it's not that simple. You want linear layout of blocks you are going to read. That is not necessary a linear layout of blocks in a single file - trace sometime a start of some complicated app like KDE. You find it's seeking like a hell because it needs a few blocks from a ton of distinct files (shared libs, config files, etc). As these files are mostly read only, it's advantageous to interleave them on disk or at least keep them close. Honza -- Jan Kara SuSE CR Labs