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writeback: do strict bdi dirty_exceeded 

This helps to reduce dirty throttling polls and hence CPU overheads.

bdi->dirty_exceeded typically only helps when suddenly starting 100+
dd's on a disk, in which case the dd's may need to poll
balance_dirty_pages() earlier than tsk->nr_dirtied_pause.

CC: Jan Kara <jack@suse.cz>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
This commit is contained in:
Wu Fengguang 2011-12-03 21:26:01 -06:00
parent 5b9b357435
commit 8279194054
1 changed files with 1 additions and 1 deletions
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2
mm/page-writeback.c
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@ -1160,7 +1160,7 @@ static void balance_dirty_pages(struct address_space *mapping,
bdi_stat(bdi, BDI_WRITEBACK);
}
dirty_exceeded = (bdi_dirty > bdi_thresh) ||
dirty_exceeded = (bdi_dirty > bdi_thresh) &&
(nr_dirty > dirty_thresh);
if (dirty_exceeded && !bdi->dirty_exceeded)
bdi->dirty_exceeded = 1;