From: Peter Zijlstra Subject: mm: speed up writeback ramp-up on clean systems We allow violation of bdi limits if there is a lot of room on the system. Once we hit half the total limit we start enforcing bdi limits and bdi ramp-up should happen. Doing it this way avoids many small writeouts on an otherwise idle system and should also speed up the ramp-up. Signed-off-by: Peter Zijlstra Signed-off-by: Fengguang Wu --- mm/page-writeback.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) --- linux-2.6.24-git17.orig/mm/page-writeback.c +++ linux-2.6.24-git17/mm/page-writeback.c @@ -355,8 +355,8 @@ get_dirty_limits(long *pbackground, long */ static void balance_dirty_pages(struct address_space *mapping) { - long bdi_nr_reclaimable; - long bdi_nr_writeback; + long nr_reclaimable, bdi_nr_reclaimable; + long nr_writeback, bdi_nr_writeback; long background_thresh; long dirty_thresh; long bdi_thresh; @@ -376,11 +376,26 @@ static void balance_dirty_pages(struct a get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi); + + nr_reclaimable = global_page_state(NR_FILE_DIRTY) + + global_page_state(NR_UNSTABLE_NFS); + nr_writeback = global_page_state(NR_WRITEBACK); + bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); + if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) break; + /* + * Throttle it only when the background writeback cannot + * catch-up. This avoids (excessively) small writeouts + * when the bdi limits are ramping up. + */ + if (nr_reclaimable + nr_writeback < + (background_thresh + dirty_thresh) / 2) + break; + if (!bdi->dirty_exceeded) bdi->dirty_exceeded = 1;