diff options
| -rw-r--r-- | mm/page-writeback.c | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 5830991f261a..422cf4edab47 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -42,6 +42,12 @@ #define MAX_PAUSE max(HZ/5, 1) /* + * Try to keep balance_dirty_pages() call intervals higher than this many pages + * by raising pause time to max_pause when falls below it. + */ +#define DIRTY_POLL_THRESH (128 >> (PAGE_SHIFT - 10)) + +/* * Estimate write bandwidth at 200ms intervals. */ #define BANDWIDTH_INTERVAL max(HZ/5, 1) @@ -1026,6 +1032,23 @@ static long bdi_min_pause(struct backing_dev_info *bdi, t = min(t, 1 + max_pause / 2); pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); + /* + * Tiny nr_dirtied_pause is found to hurt I/O performance in the test + * case fio-mmap-randwrite-64k, which does 16*{sync read, async write}. + * When the 16 consecutive reads are often interrupted by some dirty + * throttling pause during the async writes, cfq will go into idles + * (deadline is fine). So push nr_dirtied_pause as high as possible + * until reaches DIRTY_POLL_THRESH=32 pages. + */ + if (pages < DIRTY_POLL_THRESH) { + t = max_pause; + pages = dirty_ratelimit * t / roundup_pow_of_two(HZ); + if (pages > DIRTY_POLL_THRESH) { + pages = DIRTY_POLL_THRESH; + t = HZ * DIRTY_POLL_THRESH / dirty_ratelimit; + } + } + pause = HZ * pages / (task_ratelimit + 1); if (pause > max_pause) { t = max_pause; @@ -1036,7 +1059,7 @@ static long bdi_min_pause(struct backing_dev_info *bdi, /* * The minimal pause time will normally be half the target pause time. */ - return 1 + t / 2; + return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t; } /* |