diff options
Diffstat (limited to 'mm/page-writeback.c')
| -rw-r--r-- | mm/page-writeback.c | 55 |
1 files changed, 35 insertions, 20 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index a3278f005230..50f08241f981 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -128,7 +128,6 @@ unsigned long global_dirty_limit; * */ static struct prop_descriptor vm_completions; -static struct prop_descriptor vm_dirties; /* * couple the period to the dirty_ratio: @@ -154,7 +153,6 @@ static void update_completion_period(void) { int shift = calc_period_shift(); prop_change_shift(&vm_completions, shift); - prop_change_shift(&vm_dirties, shift); writeback_set_ratelimit(); } @@ -235,11 +233,6 @@ void bdi_writeout_inc(struct backing_dev_info *bdi) } EXPORT_SYMBOL_GPL(bdi_writeout_inc); -void task_dirty_inc(struct task_struct *tsk) -{ - prop_inc_single(&vm_dirties, &tsk->dirties); -} - /* * Obtain an accurate fraction of the BDI's portion. */ @@ -418,8 +411,13 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) * * Returns @bdi's dirty limit in pages. The term "dirty" in the context of * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages. - * And the "limit" in the name is not seriously taken as hard limit in - * balance_dirty_pages(). + * + * Note that balance_dirty_pages() will only seriously take it as a hard limit + * when sleeping max_pause per page is not enough to keep the dirty pages under + * control. For example, when the device is completely stalled due to some error + * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key. + * In the other normal situations, it acts more gently by throttling the tasks + * more (rather than completely block them) when the bdi dirty pages go high. * * It allocates high/low dirty limits to fast/slow devices, in order to prevent * - starving fast devices @@ -601,6 +599,13 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi, */ if (unlikely(bdi_thresh > thresh)) bdi_thresh = thresh; + /* + * It's very possible that bdi_thresh is close to 0 not because the + * device is slow, but that it has remained inactive for long time. + * Honour such devices a reasonable good (hopefully IO efficient) + * threshold, so that the occasional writes won't be blocked and active + * writes can rampup the threshold quickly. + */ bdi_thresh = max(bdi_thresh, (limit - dirty) / 8); /* * scale global setpoint to bdi's: @@ -984,8 +989,7 @@ static unsigned long bdi_max_pause(struct backing_dev_info *bdi, * * 8 serves as the safety ratio. */ - if (bdi_dirty) - t = min(t, bdi_dirty * HZ / (8 * bw + 1)); + t = min(t, bdi_dirty * HZ / (8 * bw + 1)); /* * The pause time will be settled within range (max_pause/4, max_pause). @@ -1133,17 +1137,30 @@ pause: pages_dirtied, pause, start_time); - __set_current_state(TASK_UNINTERRUPTIBLE); + __set_current_state(TASK_KILLABLE); io_schedule_timeout(pause); - 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. + * This is typically equal to (nr_dirty < dirty_thresh) and can + * also keep "1000+ dd on a slow USB stick" under control. */ - if (nr_dirty < dirty_thresh) + if (task_ratelimit) + break; + + /* + * In the case of an unresponding NFS server and the NFS dirty + * pages exceeds dirty_thresh, give the other good bdi's a pipe + * to go through, so that tasks on them still remain responsive. + * + * In theory 1 page is enough to keep the comsumer-producer + * pipe going: the flusher cleans 1 page => the task dirties 1 + * more page. However bdi_dirty has accounting errors. So use + * the larger and more IO friendly bdi_stat_error. + */ + if (bdi_dirty <= bdi_stat_error(bdi)) + break; + + if (fatal_signal_pending(current)) break; } @@ -1395,7 +1412,6 @@ void __init page_writeback_init(void) shift = calc_period_shift(); prop_descriptor_init(&vm_completions, shift); - prop_descriptor_init(&vm_dirties, shift); } /** @@ -1724,7 +1740,6 @@ void account_page_dirtied(struct page *page, struct address_space *mapping) __inc_zone_page_state(page, NR_DIRTIED); __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); - task_dirty_inc(current); task_io_account_write(PAGE_CACHE_SIZE); } } |