From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Wed, 11 Oct 2006 09:53:47 -0700 (PDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.168.28]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id k9BGrbaG025702 for ; Wed, 11 Oct 2006 09:53:38 -0700 Message-ID: <452D2086.2020204@xfs.org> Date: Wed, 11 Oct 2006 11:49:10 -0500 From: Steve Lord MIME-Version: 1.0 Subject: Re: Directories > 2GB References: <20061004165655.GD22010@schatzie.adilger.int> <452AC4BE.6090905@xfs.org> <20061010015512.GQ11034@melbourne.sgi.com> <452B0240.60203@xfs.org> <20061010091904.GA395@infradead.org> <20061010233124.GX11034@melbourne.sgi.com> In-Reply-To: <20061010233124.GX11034@melbourne.sgi.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: David Chinner Cc: Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com David Chinner wrote: > On Tue, Oct 10, 2006 at 10:19:04AM +0100, Christoph Hellwig wrote: >> On Mon, Oct 09, 2006 at 09:15:28PM -0500, Steve Lord wrote: >>> Hi Dave, >>> >>> My recollection is that it used to default to on, it was disabled >>> because it needs to map the buffer into a single contiguous chunk >>> of kernel memory. This was placing a lot of pressure on the memory >>> remapping code, so we made it not default to on as reworking the >>> code to deal with non contig memory was looking like a major >>> effort. >> Exactly. The code works but tends to go OOM pretty fast at least >> when the dir blocksize code is bigger than the page size. I should >> give the code a spin on my ppc box with 64k pages if it works better >> there. > > The pagebuf code doesn't use high-order allocations anymore; it uses > scatter lists and remapping to allow physically discontiguous pages > in a multi-page buffer. That is, the pages are sourced via > find_or_create_page() from the address space of the backing device, > and then mapped via vmap() to provide a virtually contigous mapping > of the multi-page buffer. > > So I don't think this problem exists anymore... I was not referring to high order allocations here, but the overhead of doing address space remapping every time a directory is accessed. Steve