Commit 5fce25a9 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds

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: default avatarPeter Zijlstra <>
Reviewed-by: default avatarFengguang Wu <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 546040dc
......@@ -355,8 +355,8 @@ get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty,
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 address_space *mapping)
get_dirty_limits(&background_thresh, &dirty_thresh,
&bdi_thresh, bdi);
nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
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)
* 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)
if (!bdi->dirty_exceeded)
bdi->dirty_exceeded = 1;
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