From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 85C266B004A for ; Tue, 14 Sep 2010 05:17:25 -0400 (EDT) Date: Tue, 14 Sep 2010 17:17:20 +0800 From: Wu Fengguang Subject: Re: [PATCH 05/17] writeback: quit throttling when signal pending Message-ID: <20100914091720.GA23042@localhost> References: <20100914172028.C9B2.A69D9226@jp.fujitsu.com> <20100914083338.GA20295@localhost> <20100914174017.C9BB.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100914174017.C9BB.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Neil Brown , linux-mm , LKML , Andrew Morton , Theodore Ts'o , Dave Chinner , Jan Kara , Peter Zijlstra , Mel Gorman , Rik van Riel , Chris Mason , Christoph Hellwig , "Li, Shaohua" List-ID: On Tue, Sep 14, 2010 at 04:44:37PM +0800, KOSAKI Motohiro wrote: > > On Tue, Sep 14, 2010 at 04:23:56PM +0800, KOSAKI Motohiro wrote: > > > > Subject: writeback: quit throttling when fatal signal pending > > > > From: Wu Fengguang > > > > Date: Wed Sep 08 17:40:22 CST 2010 > > > > > > > > This allows quick response to Ctrl-C etc. for impatient users. > > > > > > > > It mainly helps the rare bdi/global dirty exceeded cases. > > > > In the normal case of not exceeded, it will quit the loop anyway. > > > > > > > > CC: Neil Brown > > > > Signed-off-by: Wu Fengguang > > > > --- > > > > mm/page-writeback.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > --- linux-next.orig/mm/page-writeback.c 2010-09-12 13:25:23.000000000 +0800 > > > > +++ linux-next/mm/page-writeback.c 2010-09-13 11:39:33.000000000 +0800 > > > > @@ -552,6 +552,9 @@ static void balance_dirty_pages(struct a > > > > __set_current_state(TASK_INTERRUPTIBLE); > > > > io_schedule_timeout(pause); > > > > > > > > + if (fatal_signal_pending(current)) > > > > + break; > > > > + > > > > check_exceeded: > > > > /* > > > > * The bdi thresh is somehow "soft" limit derived from the > > > > > > I think we need to change callers (e.g. generic_perform_write) too. > > > Otherwise, plenty write + SIGKILL combination easily exceed dirty limit. > > > It mean we can see strange OOM. > > > > If it's dangerous, we can do without this patch. > > How? As you described. > > The users can still > > get quick response in normal case after all. > > > > However, I suspect the process is guaranteed to exit on > > fatal_signal_pending, so it won't dirty more pages :) > > Process exiting is delayed until syscall exiting. So, we exit write syscall > manually if necessary. Got it, you mean this fix. It looks good. I didn't add "status = -EINTR" in the patch because the bottom line "written ? : status" will always select the non-zero written. diff --git a/mm/filemap.c b/mm/filemap.c index 3d4df44..f6d2740 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2304,7 +2304,8 @@ again: written += copied; balance_dirty_pages_ratelimited(mapping); - + if (fatal_signal_pending(current)) + break; } while (iov_iter_count(i)); return written ? written : status; Thanks, Fengguang -- 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