On Wed 09-03-11 19:07:31, Vivek Goyal wrote:
> > +static void balance_dirty_pages(struct address_space *mapping,
> > + unsigned long write_chunk)
> > +{
> > + struct backing_dev_info *bdi = mapping->backing_dev_info;
> > + struct balance_waiter bw;
> > + struct dirty_limit_state st;
> > + int dirty_exceeded = check_dirty_limits(bdi, &st);
> > +
> > + if (dirty_exceeded < DIRTY_MAY_EXCEED_LIMIT ||
> > + (dirty_exceeded == DIRTY_MAY_EXCEED_LIMIT &&
> > + !bdi_task_limit_exceeded(&st, current))) {
> > + if (bdi->dirty_exceeded &&
> > + dirty_exceeded < DIRTY_MAY_EXCEED_LIMIT)
> > + bdi->dirty_exceeded = 0;
> > /*
> > - * Increase the delay for each loop, up to our previous
> > - * default of taking a 100ms nap.
> > + * In laptop mode, we wait until hitting the higher threshold
> > + * before starting background writeout, and then write out all
> > + * the way down to the lower threshold. So slow writers cause
> > + * minimal disk activity.
> > + *
> > + * In normal mode, we start background writeout at the lower
> > + * background_thresh, to keep the amount of dirty memory low.
> > */
> > - pause <<= 1;
> > - if (pause > HZ / 10)
> > - pause = HZ / 10;
> > + if (!laptop_mode && dirty_exceeded == DIRTY_EXCEED_BACKGROUND)
> > + bdi_start_background_writeback(bdi);
> > + return;
> > }
> >
> > - /* Clear dirty_exceeded flag only when no task can exceed the limit */
> > - if (!min_dirty_exceeded && bdi->dirty_exceeded)
> > - bdi->dirty_exceeded = 0;
> > + if (!bdi->dirty_exceeded)
> > + bdi->dirty_exceeded = 1;
>
> Will it make sense to move out bdi_task_limit_exceeded() check in a
> separate if condition statement as follows. May be this is little
> easier to read.
>
> if (dirty_exceeded < DIRTY_MAY_EXCEED_LIMIT) {
> if (bdi->dirty_exceeded)
> bdi->dirty_exceeded = 0;
>
> if (!laptop_mode && dirty_exceeded == DIRTY_EXCEED_BACKGROUND)
> bdi_start_background_writeback(bdi);
>
> return;
> }
>
> if (dirty_exceeded == DIRTY_MAY_EXCEED_LIMIT &&
> !bdi_task_limit_exceeded(&st, current))
> return;
But then we have to start background writeback here as well. Which is
actually a bug in the original patch as well! So clearly your way is more
readable :) I'll change it. Thanks.
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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