From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 4D5416B004A for ; Thu, 14 Jul 2011 11:07:10 -0400 (EDT) Date: Thu, 14 Jul 2011 11:07:00 -0400 From: Christoph Hellwig Subject: Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim Message-ID: <20110714150700.GC23587@infradead.org> References: <1310567487-15367-1-git-send-email-mgorman@suse.de> <1310567487-15367-2-git-send-email-mgorman@suse.de> <20110714103801.83e10fdb.kamezawa.hiroyu@jp.fujitsu.com> <20110714044643.GA3203@infradead.org> <20110714134634.4a7a15c8.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110714134634.4a7a15c8.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: Christoph Hellwig , Mel Gorman , Linux-MM , LKML , XFS , Dave Chinner , Johannes Weiner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim On Thu, Jul 14, 2011 at 01:46:34PM +0900, KAMEZAWA Hiroyuki wrote: > > XFS and btrfs already disable writeback from memcg context, as does ext4 > > for the typical non-overwrite workloads, and none has fallen apart. > > > > In fact there's no way we can enable them as the memcg calling contexts > > tend to have massive stack usage. > > > > Hmm, XFS/btrfs adds pages to radix-tree in deep stack ? We're using a fairly deep stack in normal buffered read/write, wich is almost 100% common code. It's not just the long callchain (see below), but also that we put the unneeded kiocb and a vector of I/O vects on the stack: vfs_writev do_readv_writev do_sync_write generic_file_aio_write __generic_file_aio_write generic_file_buffered_write generic_perform_write block_write_begin grab_cache_page_write_begin add_to_page_cache_lru add_to_page_cache add_to_page_cache_locked mem_cgroup_cache_charge this might additionally come from in-kernel callers like nfsd, which has even more stack space used. And at this point we only enter the memcg/reclaim code, which last time I had a stack trace ate up another about 3k of stack space. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org