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mm: Move starting of background writeback into the main balancing loop

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We start background writeback if we are over background threshold after
exiting the main loop in balance_dirty_pages(). This may result in
basing the decision on already stale values (we may have slept for
significant amount of time) and it is also inconvenient for refactoring
needed for async dirty throttling. Move the check into the main waiting
loop.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Stefan Roesch <shr@fb.com>
Link: https://lore.kernel.org/r/20220623175157.1715274-2-shr@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jan Kara 2022-06-23 10:51:44 -07:00 committed by Jens Axboe
parent f6b543fd03
commit ea6813be07
1 changed files with 14 additions and 17 deletions
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31
mm/page-writeback.c
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@ -1627,6 +1627,19 @@ static void balance_dirty_pages(struct bdi_writeback *wb,
}
}
/*
* 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.
*/
if (!laptop_mode && nr_reclaimable > gdtc->bg_thresh &&
!writeback_in_progress(wb))
wb_start_background_writeback(wb);
/*
* Throttle it only when the background writeback cannot
* catch-up. This avoids (excessively) small writeouts
@ -1657,6 +1670,7 @@ static void balance_dirty_pages(struct bdi_writeback *wb,
break;
}
/* Start writeback even when in laptop mode */
if (unlikely(!writeback_in_progress(wb)))
wb_start_background_writeback(wb);
@ -1823,23 +1837,6 @@ static void balance_dirty_pages(struct bdi_writeback *wb,
if (!dirty_exceeded && wb->dirty_exceeded)
wb->dirty_exceeded = 0;
if (writeback_in_progress(wb))
return;
/*
* 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.
*/
if (laptop_mode)
return;
if (nr_reclaimable > gdtc->bg_thresh)
wb_start_background_writeback(wb);
}
static DEFINE_PER_CPU(int, bdp_ratelimits);