Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933413Ab0GOOvG (ORCPT ); Thu, 15 Jul 2010 10:51:06 -0400 Received: from mga03.intel.com ([143.182.124.21]:51494 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933382Ab0GOOvE (ORCPT ); Thu, 15 Jul 2010 10:51:04 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.55,208,1278313200"; d="scan'208";a="300537641" Date: Thu, 15 Jul 2010 22:50:45 +0800 From: Wu Fengguang To: Miklos Szeredi Cc: Andrew Morton , "hch@infradead.org" , "richard@rsk.demon.co.uk" , "david@fromorbit.com" , "jack@suse.cz" , "a.p.zijlstra@chello.nl" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/6] writeback: take account of NR_WRITEBACK_TEMP in balance_dirty_pages() Message-ID: <20100715145045.GA6511@localhost> References: <20100711020656.340075560@intel.com> <20100711021748.594522648@intel.com> <20100712145206.9808b411.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2837 Lines: 72 On Tue, Jul 13, 2010 at 04:58:47PM +0800, Miklos Szeredi wrote: > On Mon, 12 Jul 2010, Andrew Morton wrote: > > On Sun, 11 Jul 2010 10:06:57 +0800 > > Wu Fengguang wrote: > > > > > > > > Signed-off-by: Richard Kennedy > > > Signed-off-by: Wu Fengguang > > > --- > > > mm/page-writeback.c | 7 ++++--- > > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > > > --- linux-next.orig/mm/page-writeback.c 2010-07-11 08:41:37.000000000 +0800 > > > +++ linux-next/mm/page-writeback.c 2010-07-11 08:42:14.000000000 +0800 > > > @@ -503,11 +503,12 @@ static void balance_dirty_pages(struct a > > > }; > > > > > > get_dirty_limits(&background_thresh, &dirty_thresh, > > > - &bdi_thresh, bdi); > > > + &bdi_thresh, bdi); > > > > > > nr_reclaimable = global_page_state(NR_FILE_DIRTY) + > > > - global_page_state(NR_UNSTABLE_NFS); > > > - nr_writeback = global_page_state(NR_WRITEBACK); > > > + global_page_state(NR_UNSTABLE_NFS); > > > + nr_writeback = global_page_state(NR_WRITEBACK) + > > > + global_page_state(NR_WRITEBACK_TEMP); > > > > > > bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); > > > bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); > > > > > > > hm, OK. > > Hm, hm. I'm not sure this is right. The VM has absolutely no control > over NR_WRITEBACK_TEMP pages, they may clear quickly or may not make > any progress. So it's usually wrong to make a decision based on > NR_WRITEBACK_TEMP for an unrelated device. Ah OK, let's remove this patch. > Using it in throttle_vm_writeout() would actually be deadlocky, since > the userspace filesystem will probably depend on memory allocations to > complete the writeout. Right. > The only place where we should be taking NR_WRITEBACK_TEMP into > account is calculating the remaining memory that can be devided > between dirtyers, and that's (clip_bdi_dirty_limit) where it is > already used. clip_bdi_dirty_limit() is removed in the next patch, hopefully it's OK. > > I wonder whether we could/should have unified NR_WRITEBACK_TEMP and > > NR_UNSTABLE_NFS. Their "meanings" aren't quite the same, but perhaps > > some "treat page as dirty because the fs is futzing with it" thing. > > AFAICS NR_UNSTABLE_NFS is something akin to NR_DIRTY, only on the > server side. So nfs can very much do something about making > NR_UNSTABLE_NFS go away, while there's nothing that can be done about > NR_WRITEBACK_TEMP. Right. nfs_write_inode() normally tries to commit unstable pages. Thanks, Fengguang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/