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-rw-r--r--mm/page-writeback.c31
1 files changed, 28 insertions, 3 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 1ea13ef350a8..20890d80c7ef 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -261,11 +261,18 @@ static inline void task_dirties_fraction(struct task_struct *tsk,
261} 261}
262 262
263/* 263/*
264 * scale the dirty limit 264 * task_dirty_limit - scale down dirty throttling threshold for one task
265 * 265 *
266 * task specific dirty limit: 266 * task specific dirty limit:
267 * 267 *
268 * dirty -= (dirty/8) * p_{t} 268 * dirty -= (dirty/8) * p_{t}
269 *
270 * To protect light/slow dirtying tasks from heavier/fast ones, we start
271 * throttling individual tasks before reaching the bdi dirty limit.
272 * Relatively low thresholds will be allocated to heavy dirtiers. So when
273 * dirty pages grow large, heavy dirtiers will be throttled first, which will
274 * effectively curb the growth of dirty pages. Light dirtiers with high enough
275 * dirty threshold may never get throttled.
269 */ 276 */
270static unsigned long task_dirty_limit(struct task_struct *tsk, 277static unsigned long task_dirty_limit(struct task_struct *tsk,
271 unsigned long bdi_dirty) 278 unsigned long bdi_dirty)
@@ -390,6 +397,15 @@ unsigned long determine_dirtyable_memory(void)
390 return x + 1; /* Ensure that we never return 0 */ 397 return x + 1; /* Ensure that we never return 0 */
391} 398}
392 399
400/**
401 * global_dirty_limits - background-writeback and dirty-throttling thresholds
402 *
403 * Calculate the dirty thresholds based on sysctl parameters
404 * - vm.dirty_background_ratio or vm.dirty_background_bytes
405 * - vm.dirty_ratio or vm.dirty_bytes
406 * The dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
407 * runtime tasks.
408 */
393void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) 409void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
394{ 410{
395 unsigned long background; 411 unsigned long background;
@@ -424,8 +440,17 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
424 *pdirty = dirty; 440 *pdirty = dirty;
425} 441}
426 442
427unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, 443/**
428 unsigned long dirty) 444 * bdi_dirty_limit - @bdi's share of dirty throttling threshold
445 *
446 * Allocate high/low dirty limits to fast/slow devices, in order to prevent
447 * - starving fast devices
448 * - piling up dirty pages (that will take long time to sync) on slow devices
449 *
450 * The bdi's share of dirty limit will be adapting to its throughput and
451 * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
452 */
453unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
429{ 454{
430 u64 bdi_dirty; 455 u64 bdi_dirty;
431 long numerator, denominator; 456 long numerator, denominator;