diff options
| -rw-r--r-- | mm/page-writeback.c | 95 |
1 files changed, 33 insertions, 62 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index ea0b7cb4a8c7..2cf69a5e46e6 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -253,32 +253,6 @@ static void bdi_writeout_fraction(struct backing_dev_info *bdi, } } -/* - * Clip the earned share of dirty pages to that which is actually available. - * This avoids exceeding the total dirty_limit when the floating averages - * fluctuate too quickly. - */ -static void clip_bdi_dirty_limit(struct backing_dev_info *bdi, - unsigned long dirty, unsigned long *pbdi_dirty) -{ - unsigned long avail_dirty; - - avail_dirty = global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_WRITEBACK) + - global_page_state(NR_UNSTABLE_NFS) + - global_page_state(NR_WRITEBACK_TEMP); - - if (avail_dirty < dirty) - avail_dirty = dirty - avail_dirty; - else - avail_dirty = 0; - - avail_dirty += bdi_stat(bdi, BDI_RECLAIMABLE) + - bdi_stat(bdi, BDI_WRITEBACK); - - *pbdi_dirty = min(*pbdi_dirty, avail_dirty); -} - static inline void task_dirties_fraction(struct task_struct *tsk, long *numerator, long *denominator) { @@ -469,7 +443,6 @@ get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty, bdi_dirty = dirty * bdi->max_ratio / 100; *pbdi_dirty = bdi_dirty; - clip_bdi_dirty_limit(bdi, dirty, pbdi_dirty); task_dirty_limit(current, pbdi_dirty); } } @@ -491,7 +464,7 @@ static void balance_dirty_pages(struct address_space *mapping, unsigned long bdi_thresh; unsigned long pages_written = 0; unsigned long pause = 1; - + bool dirty_exceeded = false; struct backing_dev_info *bdi = mapping->backing_dev_info; for (;;) { @@ -509,10 +482,35 @@ static void balance_dirty_pages(struct address_space *mapping, global_page_state(NR_UNSTABLE_NFS); nr_writeback = global_page_state(NR_WRITEBACK); - bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); - bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); + /* + * In order to avoid the stacked BDI deadlock we need + * to ensure we accurately count the 'dirty' pages when + * the threshold is low. + * + * Otherwise it would be possible to get thresh+n pages + * reported dirty, even though there are thresh-m pages + * actually dirty; with m+n sitting in the percpu + * deltas. + */ + if (bdi_thresh < 2*bdi_stat_error(bdi)) { + bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); + bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); + } else { + bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); + bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); + } - if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) + /* + * The bdi thresh is somehow "soft" limit derived from the + * global "hard" limit. The former helps to prevent heavy IO + * bdi or process from holding back light ones; The latter is + * the last resort safeguard. + */ + dirty_exceeded = + (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh) + || (nr_reclaimable + nr_writeback >= dirty_thresh); + + if (!dirty_exceeded) break; /* @@ -540,34 +538,10 @@ static void balance_dirty_pages(struct address_space *mapping, if (bdi_nr_reclaimable > bdi_thresh) { writeback_inodes_wb(&bdi->wb, &wbc); pages_written += write_chunk - wbc.nr_to_write; - get_dirty_limits(&background_thresh, &dirty_thresh, - &bdi_thresh, bdi); trace_wbc_balance_dirty_written(&wbc, bdi); + if (pages_written >= write_chunk) + break; /* We've done our duty */ } - - /* - * In order to avoid the stacked BDI deadlock we need - * to ensure we accurately count the 'dirty' pages when - * the threshold is low. - * - * Otherwise it would be possible to get thresh+n pages - * reported dirty, even though there are thresh-m pages - * actually dirty; with m+n sitting in the percpu - * deltas. - */ - if (bdi_thresh < 2*bdi_stat_error(bdi)) { - bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE); - bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK); - } else if (bdi_nr_reclaimable) { - bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE); - bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); - } - - if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) - break; - if (pages_written >= write_chunk) - break; /* We've done our duty */ - trace_wbc_balance_dirty_wait(&wbc, bdi); __set_current_state(TASK_INTERRUPTIBLE); io_schedule_timeout(pause); @@ -581,8 +555,7 @@ static void balance_dirty_pages(struct address_space *mapping, pause = HZ / 10; } - if (bdi_nr_reclaimable + bdi_nr_writeback < bdi_thresh && - bdi->dirty_exceeded) + if (!dirty_exceeded && bdi->dirty_exceeded) bdi->dirty_exceeded = 0; if (writeback_in_progress(bdi)) @@ -597,9 +570,7 @@ static void balance_dirty_pages(struct address_space *mapping, * background_thresh, to keep the amount of dirty memory low. */ if ((laptop_mode && pages_written) || - (!laptop_mode && ((global_page_state(NR_FILE_DIRTY) - + global_page_state(NR_UNSTABLE_NFS)) - > background_thresh))) + (!laptop_mode && (nr_reclaimable > background_thresh))) bdi_start_background_writeback(bdi); } |