diff options
| -rw-r--r-- | include/linux/writeback.h | 21 | ||||
| -rw-r--r-- | mm/page-writeback.c | 33 |
2 files changed, 54 insertions, 0 deletions
diff --git a/include/linux/writeback.h b/include/linux/writeback.h index e9d371b6053..b625073b80c 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -7,6 +7,27 @@ #include <linux/sched.h> #include <linux/fs.h> +/* + * The 1/16 region above the global dirty limit will be put to maximum pauses: + * + * (limit, limit + limit/DIRTY_MAXPAUSE_AREA) + * + * The 1/16 region above the max-pause region, dirty exceeded bdi's will be put + * to loops: + * + * (limit + limit/DIRTY_MAXPAUSE_AREA, limit + limit/DIRTY_PASSGOOD_AREA) + * + * Further beyond, all dirtier tasks will enter a loop waiting (possibly long + * time) for the dirty pages to drop, unless written enough pages. + * + * The global dirty threshold is normally equal to the global dirty limit, + * except when the system suddenly allocates a lot of anonymous memory and + * knocks down the global dirty threshold quickly, in which case the global + * dirty limit will follow down slowly to prevent livelocking all dirtier tasks. + */ +#define DIRTY_MAXPAUSE_AREA 16 +#define DIRTY_PASSGOOD_AREA 8 + struct backing_dev_info; /* diff --git a/mm/page-writeback.c b/mm/page-writeback.c index da959952b9f..798842a2247 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -37,6 +37,11 @@ #include <trace/events/writeback.h> /* + * Sleep at most 200ms at a time in balance_dirty_pages(). + */ +#define MAX_PAUSE max(HZ/5, 1) + +/* * Estimate write bandwidth at 200ms intervals. */ #define BANDWIDTH_INTERVAL max(HZ/5, 1) @@ -399,6 +404,11 @@ unsigned long determine_dirtyable_memory(void) return x + 1; /* Ensure that we never return 0 */ } +static unsigned long hard_dirty_limit(unsigned long thresh) +{ + return max(thresh, global_dirty_limit); +} + /* * global_dirty_limits - background-writeback and dirty-throttling thresholds * @@ -723,6 +733,29 @@ static void balance_dirty_pages(struct address_space *mapping, io_schedule_timeout(pause); trace_balance_dirty_wait(bdi); + dirty_thresh = hard_dirty_limit(dirty_thresh); + /* + * max-pause area. If dirty exceeded but still within this + * area, no need to sleep for more than 200ms: (a) 8 pages per + * 200ms is typically more than enough to curb heavy dirtiers; + * (b) the pause time limit makes the dirtiers more responsive. + */ + if (nr_dirty < dirty_thresh + + dirty_thresh / DIRTY_MAXPAUSE_AREA && + time_after(jiffies, start_time + MAX_PAUSE)) + break; + /* + * pass-good area. When some bdi gets blocked (eg. NFS server + * not responding), or write bandwidth dropped dramatically due + * to concurrent reads, or dirty threshold suddenly dropped and + * the dirty pages cannot be brought down anytime soon (eg. on + * slow USB stick), at least let go of the good bdi's. + */ + if (nr_dirty < dirty_thresh + + dirty_thresh / DIRTY_PASSGOOD_AREA && + bdi_dirty < bdi_thresh) + break; + /* * Increase the delay for each loop, up to our previous * default of taking a 100ms nap. |