From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim and use a_ops->writepages() where possible Date: Fri, 11 Jun 2010 15:12:32 -0400 Message-ID: <20100611191232.GZ4366@think.oraclecorp.com> References: <1275987745-21708-1-git-send-email-mel@csn.ul.ie> <20100608090811.GA5949@infradead.org> <20100608092814.GB27717@csn.ul.ie> <20100611162912.GC24707@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mel Gorman , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Nick Piggin , Rik van Riel To: Christoph Hellwig Return-path: Content-Disposition: inline In-Reply-To: <20100611162912.GC24707@infradead.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Jun 11, 2010 at 12:29:12PM -0400, Christoph Hellwig wrote: > On Tue, Jun 08, 2010 at 10:28:14AM +0100, Mel Gorman wrote: > > > - we also need to care about ->releasepage. At least for XFS it > > > can end up in the same deep allocator chain as ->writepage because > > > it does all the extent state conversions, even if it doesn't > > > start I/O. > > > > Dang. > > > > > I haven't managed yet to decode the ext4/btrfs codepaths > > > for ->releasepage yet to figure out how they release a page that > > > covers a delayed allocated or unwritten range. > > > > > > > If ext4/btrfs are also very deep call-chains and this series is going more > > or less the right direction, then avoiding calling ->releasepage from direct > > reclaim is one, somewhat unfortunate, option. The second is to avoid it on > > a per-filesystem basis for direct reclaim using PF_MEMALLOC to detect > > reclaimers and PF_KSWAPD to tell the difference between direct > > reclaimers and kswapd. > > I went throught this a bit more and I can't actually hit that code in > XFS ->releasepage anymore. I've also audited the caller and can't see > how we could theoretically hit it anymore. Do the VM gurus know a case > where we would call ->releasepage on a page that's actually dirty and > hasn't been through block_invalidatepage before? Which part of xfs releasepage are you trying to avoid? dirty = xfs_page_state_convert(inode, page, &wbc, 0, 0); if (dirty == 0 && !unwritten) goto free_buffers; I'd expect the above was fixed by page_mkwrite, which should be dealing with all the funny corners that we used to have to mess with in releasepage. btrfs_release_page does no allocations, it only checks to see if the page is busy somehow (dirty/writeback etc). -chris -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org