From: Chris Mason Subject: Re: [PATCH] ext2: Use page_mkwrite vma_operations to get mmap write notification. Date: Thu, 12 Jun 2008 08:22:43 -0400 Message-ID: <1213273364.10187.281.camel@think.oraclecorp.com> References: <1212685513-32237-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20080605123045.445e380a.akpm@linux-foundation.org> <20080611150845.GA21910@skywalker> <20080611120749.d0c5a7de.akpm@linux-foundation.org> <20080612040643.GA5518@skywalker> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Andrew Morton , cmm@us.ibm.com, jack@suse.cz, linux-ext4@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org To: "Aneesh Kumar K.V" Return-path: Received: from agminet01.oracle.com ([141.146.126.228]:14774 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760082AbYFLMac (ORCPT ); Thu, 12 Jun 2008 08:30:32 -0400 In-Reply-To: <20080612040643.GA5518@skywalker> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, 2008-06-12 at 09:36 +0530, Aneesh Kumar K.V wrote: > On Wed, Jun 11, 2008 at 12:07:49PM -0700, Andrew Morton wrote: > > On Wed, 11 Jun 2008 20:38:45 +0530 > > "Aneesh Kumar K.V" wrote: > The idea is to have ext3/4_writepages. In writepages start a transaction > and iterate over the pages take the lock and do block allocation. With > that change we should be able to not do block allocation in the > page_mkwrite path. We may still want to do block reservation there. > > Something like. > > ext4_writepages() > { > journal_start() > for_each_page() Even with delayed allocation, the vast majority of the pages won't need any allocations. You'll hit delalloc, do a big chunk with the journal lock held and then do simple writepages that don't need anything special. I know the jbd journal_start is cheaper than the reiserfs one is, but it might not perform well to hold it across the long writepages loop. At least reiser saw a good boost when I stopped calling journal_begin in writepage unless the page really needed allocations. With the loop you have in mind, it is easy enough to back out and start the transaction only when required. -chris