diff options
Diffstat (limited to 'mm/page-writeback.c')
| -rw-r--r-- | mm/page-writeback.c | 107 |
1 files changed, 66 insertions, 41 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 93d8d2f..e5363f3 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -34,6 +34,7 @@ #include <linux/syscalls.h> #include <linux/buffer_head.h> /* __set_page_dirty_buffers */ #include <linux/pagevec.h> +#include <linux/timer.h> #include <trace/events/writeback.h> /* @@ -135,7 +136,20 @@ unsigned long global_dirty_limit; * measured in page writeback completions. * */ -static struct prop_descriptor vm_completions; +static struct fprop_global writeout_completions; + +static void writeout_period(unsigned long t); +/* Timer for aging of writeout_completions */ +static struct timer_list writeout_period_timer = + TIMER_DEFERRED_INITIALIZER(writeout_period, 0, 0); +static unsigned long writeout_period_time = 0; + +/* + * Length of period for aging writeout fractions of bdis. This is an + * arbitrarily chosen number. The longer the period, the slower fractions will + * reflect changes in current writeout rate. + */ +#define VM_COMPLETIONS_PERIOD_LEN (3*HZ) /* * Work out the current dirty-memory clamping and background writeout @@ -322,34 +336,6 @@ bool zone_dirty_ok(struct zone *zone) zone_page_state(zone, NR_WRITEBACK) <= limit; } -/* - * couple the period to the dirty_ratio: - * - * period/2 ~ roundup_pow_of_two(dirty limit) - */ -static int calc_period_shift(void) -{ - unsigned long dirty_total; - - if (vm_dirty_bytes) - dirty_total = vm_dirty_bytes / PAGE_SIZE; - else - dirty_total = (vm_dirty_ratio * global_dirtyable_memory()) / - 100; - return 2 + ilog2(dirty_total - 1); -} - -/* - * update the period when the dirty threshold changes. - */ -static void update_completion_period(void) -{ - int shift = calc_period_shift(); - prop_change_shift(&vm_completions, shift); - - writeback_set_ratelimit(); -} - int dirty_background_ratio_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) @@ -383,7 +369,7 @@ int dirty_ratio_handler(struct ctl_table *table, int write, ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (ret == 0 && write && vm_dirty_ratio != old_ratio) { - update_completion_period(); + writeback_set_ratelimit(); vm_dirty_bytes = 0; } return ret; @@ -398,12 +384,21 @@ int dirty_bytes_handler(struct ctl_table *table, int write, ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); if (ret == 0 && write && vm_dirty_bytes != old_bytes) { - update_completion_period(); + writeback_set_ratelimit(); vm_dirty_ratio = 0; } return ret; } +static unsigned long wp_next_time(unsigned long cur_time) +{ + cur_time += VM_COMPLETIONS_PERIOD_LEN; + /* 0 has a special meaning... */ + if (!cur_time) + return 1; + return cur_time; +} + /* * Increment the BDI's writeout completion count and the global writeout * completion count. Called from test_clear_page_writeback(). @@ -411,8 +406,19 @@ int dirty_bytes_handler(struct ctl_table *table, int write, static inline void __bdi_writeout_inc(struct backing_dev_info *bdi) { __inc_bdi_stat(bdi, BDI_WRITTEN); - __prop_inc_percpu_max(&vm_completions, &bdi->completions, - bdi->max_prop_frac); + __fprop_inc_percpu_max(&writeout_completions, &bdi->completions, + bdi->max_prop_frac); + /* First event after period switching was turned off? */ + if (!unlikely(writeout_period_time)) { + /* + * We can race with other __bdi_writeout_inc calls here but + * it does not cause any harm since the resulting time when + * timer will fire and what is in writeout_period_time will be + * roughly the same. + */ + writeout_period_time = wp_next_time(jiffies); + mod_timer(&writeout_period_timer, writeout_period_time); + } } void bdi_writeout_inc(struct backing_dev_info *bdi) @@ -431,11 +437,33 @@ EXPORT_SYMBOL_GPL(bdi_writeout_inc); static void bdi_writeout_fraction(struct backing_dev_info *bdi, long *numerator, long *denominator) { - prop_fraction_percpu(&vm_completions, &bdi->completions, + fprop_fraction_percpu(&writeout_completions, &bdi->completions, numerator, denominator); } /* + * On idle system, we can be called long after we scheduled because we use + * deferred timers so count with missed periods. + */ +static void writeout_period(unsigned long t) +{ + int miss_periods = (jiffies - writeout_period_time) / + VM_COMPLETIONS_PERIOD_LEN; + + if (fprop_new_period(&writeout_completions, miss_periods + 1)) { + writeout_period_time = wp_next_time(writeout_period_time + + miss_periods * VM_COMPLETIONS_PERIOD_LEN); + mod_timer(&writeout_period_timer, writeout_period_time); + } else { + /* + * Aging has zeroed all fractions. Stop wasting CPU on period + * updates. + */ + writeout_period_time = 0; + } +} + +/* * bdi_min_ratio keeps the sum of the minimum dirty shares of all * registered backing devices, which, for obvious reasons, can not * exceed 100%. @@ -475,7 +503,7 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio) ret = -EINVAL; } else { bdi->max_ratio = max_ratio; - bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100; + bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; } spin_unlock_bh(&bdi_lock); @@ -918,7 +946,7 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, * bdi->dirty_ratelimit = balanced_dirty_ratelimit; * * However to get a more stable dirty_ratelimit, the below elaborated - * code makes use of task_ratelimit to filter out sigular points and + * code makes use of task_ratelimit to filter out singular points and * limit the step size. * * The below code essentially only uses the relative value of @@ -941,7 +969,7 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi, * feel and care are stable dirty rate and small position error. * * |task_ratelimit - dirty_ratelimit| is used to limit the step size - * and filter out the sigular points of balanced_dirty_ratelimit. Which + * and filter out the singular points of balanced_dirty_ratelimit. Which * keeps jumping around randomly and can even leap far away at times * due to the small 200ms estimation period of dirty_rate (we want to * keep that period small to reduce time lags). @@ -1606,13 +1634,10 @@ static struct notifier_block __cpuinitdata ratelimit_nb = { */ void __init page_writeback_init(void) { - int shift; - writeback_set_ratelimit(); register_cpu_notifier(&ratelimit_nb); - shift = calc_period_shift(); - prop_descriptor_init(&vm_completions, shift); + fprop_global_init(&writeout_completions); } /** |