From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 4/5] writeback: per task dirty rate limit Date: Mon, 8 Aug 2011 22:21:23 +0800 Message-ID: <20110808142123.GB22080@localhost> References: <20110806084447.388624428@intel.com> <20110806094527.002914580@intel.com> <1312811234.10488.34.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "linux-fsdevel@vger.kernel.org" , Andrew Morton , Jan Kara , Christoph Hellwig , Dave Chinner , Greg Thelen , Minchan Kim , Vivek Goyal , Andrea Righi , linux-mm , LKML To: Peter Zijlstra Return-path: Content-Disposition: inline In-Reply-To: <1312811234.10488.34.camel@twins> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Mon, Aug 08, 2011 at 09:47:14PM +0800, Peter Zijlstra wrote: > On Sat, 2011-08-06 at 16:44 +0800, Wu Fengguang wrote: > > Add two fields to task_struct. > > > > 1) account dirtied pages in the individual tasks, for accuracy > > 2) per-task balance_dirty_pages() call intervals, for flexibility > > > > The balance_dirty_pages() call interval (ie. nr_dirtied_pause) will > > scale near-sqrt to the safety gap between dirty pages and threshold. > > > > XXX: The main problem of per-task nr_dirtied is, if 10k tasks start > > dirtying pages at exactly the same time, each task will be assigned a > > large initial nr_dirtied_pause, so that the dirty threshold will be > > exceeded long before each task reached its nr_dirtied_pause and hence > > call balance_dirty_pages(). > > > > Signed-off-by: Wu Fengguang > > --- > > include/linux/sched.h | 7 ++ > > mm/memory_hotplug.c | 3 - > > mm/page-writeback.c | 106 +++++++++------------------------------- > > 3 files changed, 32 insertions(+), 84 deletions(-) > > No fork() hooks? This way tasks inherit their parent's dirty count on > clone(). Ah good point. Here is the quick fix. Thanks, Fengguang --- --- linux-next.orig/kernel/fork.c 2011-08-08 22:11:59.000000000 +0800 +++ linux-next/kernel/fork.c 2011-08-08 22:18:05.000000000 +0800 @@ -1301,6 +1301,9 @@ static struct task_struct *copy_process( p->pdeath_signal = 0; p->exit_state = 0; + p->nr_dirtied = 0; + p->nr_dirtied_pause = 8; + /* * Ok, make it visible to the rest of the system. * We dont wake it up yet. -- 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