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 <fengguang.wu@xxxxxxxxx> > > > > 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 <neilb@xxxxxxx> > > > > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> > > > > --- > > > > 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@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>