diff options
| -rw-r--r-- | mm/page-writeback.c | 44 |
1 files changed, 42 insertions, 2 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index f32f25092c66..cc351e6f9ed9 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -939,6 +939,43 @@ static unsigned long dirty_poll_interval(unsigned long dirty, return 1; } +static unsigned long bdi_max_pause(struct backing_dev_info *bdi, + unsigned long bdi_dirty) +{ + unsigned long bw = bdi->avg_write_bandwidth; + unsigned long hi = ilog2(bw); + unsigned long lo = ilog2(bdi->dirty_ratelimit); + unsigned long t; + + /* target for 20ms max pause on 1-dd case */ + t = HZ / 50; + + /* + * Scale up pause time for concurrent dirtiers in order to reduce CPU + * overheads. + * + * (N * 20ms) on 2^N concurrent tasks. + */ + if (hi > lo) + t += (hi - lo) * (20 * HZ) / 1024; + + /* + * Limit pause time for small memory systems. If sleeping for too long + * time, a small pool of dirty/writeback pages may go empty and disk go + * idle. + * + * 8 serves as the safety ratio. + */ + if (bdi_dirty) + t = min(t, bdi_dirty * HZ / (8 * bw + 1)); + + /* + * The pause time will be settled within range (max_pause/4, max_pause). + * Apply a minimal value of 4 to get a non-zero max_pause/4. + */ + return clamp_val(t, 4, MAX_PAUSE); +} + /* * balance_dirty_pages() must be called by processes which are generating dirty * data. It looks at the number of dirty pages in the machine and will force @@ -958,6 +995,7 @@ static void balance_dirty_pages(struct address_space *mapping, unsigned long dirty_thresh; unsigned long bdi_thresh; long pause = 0; + long max_pause; bool dirty_exceeded = false; unsigned long task_ratelimit; unsigned long dirty_ratelimit; @@ -1035,18 +1073,20 @@ static void balance_dirty_pages(struct address_space *mapping, nr_dirty, bdi_thresh, bdi_dirty, start_time); + max_pause = bdi_max_pause(bdi, bdi_dirty); + dirty_ratelimit = bdi->dirty_ratelimit; pos_ratio = bdi_position_ratio(bdi, dirty_thresh, background_thresh, nr_dirty, bdi_thresh, bdi_dirty); if (unlikely(pos_ratio == 0)) { - pause = MAX_PAUSE; + pause = max_pause; goto pause; } task_ratelimit = (u64)dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT; pause = (HZ * pages_dirtied) / (task_ratelimit | 1); - pause = min_t(long, pause, MAX_PAUSE); + pause = min(pause, max_pause); pause: __set_current_state(TASK_UNINTERRUPTIBLE); |