From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 2B33C6B01B8 for ; Wed, 16 Jun 2010 06:51:41 -0400 (EDT) Message-ID: <4C18ACBB.1090002@kernel.dk> Date: Wed, 16 Jun 2010 12:51:39 +0200 From: Jens Axboe MIME-Version: 1.0 Subject: Re: [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim References: <4C17815A.8080402@redhat.com> <20100615135928.GK26788@csn.ul.ie> <4C178868.2010002@redhat.com> <20100615141601.GL26788@csn.ul.ie> <20100616091755.7121c7d3.kamezawa.hiroyu@jp.fujitsu.com> <4C181AFD.5060503@redhat.com> <20100616093958.00673123.kamezawa.hiroyu@jp.fujitsu.com> <4C182097.2070603@redhat.com> <20100616104036.b45d352b.kamezawa.hiroyu@jp.fujitsu.com> <20100616112024.5b093905.kamezawa.hiroyu@jp.fujitsu.com> <20100616051133.GC10687@infradead.org> In-Reply-To: <20100616051133.GC10687@infradead.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Christoph Hellwig Cc: KAMEZAWA Hiroyuki , Rik van Riel , Mel Gorman , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Chris Mason , Nick Piggin , Johannes Weiner , Andrew Morton List-ID: On 2010-06-16 07:11, Christoph Hellwig wrote: > On Wed, Jun 16, 2010 at 11:20:24AM +0900, KAMEZAWA Hiroyuki wrote: >> BTW, copy_from_user/copy_to_user is _real_ problem, I'm afraid following >> much more than memcg. >> >> handle_mm_fault() >> -> handle_pte_fault() >> -> do_wp_page() >> -> balance_dirty_page_rate_limited() >> -> balance_dirty_pages() >> -> writeback_inodes_wbc() >> -> writeback_inodes_wb() >> -> writeback_sb_inodes() >> -> writeback_single_inode() >> -> do_writepages() >> -> generic_write_pages() >> -> write_cache_pages() // use on-stack pagevec. >> -> writepage() > > Yes, this is a massive issue. Strangely enough I just wondered about > this callstack as balance_dirty_pages is the only place calling into the > per-bdi/sb writeback code directly instead of offloading it to the > flusher threads. It's something that should be fixed rather quickly > IMHO. write_cache_pages and other bits of this writeback code can use > quite large amounts of stack. I've had the same thought as well, bdp() should just signal a writeback instead. Much cleaner than doing cleaning from that point. -- Jens Axboe -- 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