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SubjectRe: [PATCH 05/17] writeback: quit throttling when signal pending
Date
> 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@intel.com>
> > > 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@suse.de>
> > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > > ---
> > > 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?


> 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.

Am I missing anything?




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