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-rw-r--r--mm/page-writeback.c95
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);
}