diff options
| -rw-r--r-- | fs/fs-writeback.c | 4 | ||||
| -rw-r--r-- | fs/super.c | 2 | ||||
| -rw-r--r-- | include/linux/backing-dev.h | 4 | ||||
| -rw-r--r-- | include/linux/flex_proportions.h | 101 | ||||
| -rw-r--r-- | lib/Makefile | 2 | ||||
| -rw-r--r-- | lib/flex_proportions.c | 272 | ||||
| -rw-r--r-- | mm/backing-dev.c | 6 | ||||
| -rw-r--r-- | mm/page-writeback.c | 107 |
8 files changed, 448 insertions, 50 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 8f660dd6137..50d0b78130a 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -628,8 +628,8 @@ static long writeback_sb_inodes(struct super_block *sb, } /* - * Don't bother with new inodes or inodes beeing freed, first - * kind does not need peridic writeout yet, and for the latter + * Don't bother with new inodes or inodes being freed, first + * kind does not need periodic writeout yet, and for the latter * kind writeout is handled by the freer. */ spin_lock(&inode->i_lock); diff --git a/fs/super.c b/fs/super.c index c743fb3be4b..4c5d82f56ec 100644 --- a/fs/super.c +++ b/fs/super.c @@ -320,7 +320,7 @@ static int grab_super(struct super_block *s) __releases(sb_lock) /* * grab_super_passive - acquire a passive reference - * @s: reference we are trying to grab + * @sb: reference we are trying to grab * * Tries to acquire a passive reference. This is used in places where we * cannot take an active reference but we need to ensure that the diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index b1038bd686a..489de625cd2 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -10,7 +10,7 @@ #include <linux/percpu_counter.h> #include <linux/log2.h> -#include <linux/proportions.h> +#include <linux/flex_proportions.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/sched.h> @@ -89,7 +89,7 @@ struct backing_dev_info { unsigned long dirty_ratelimit; unsigned long balanced_dirty_ratelimit; - struct prop_local_percpu completions; + struct fprop_local_percpu completions; int dirty_exceeded; unsigned int min_ratio; diff --git a/include/linux/flex_proportions.h b/include/linux/flex_proportions.h new file mode 100644 index 00000000000..4ebc49fae39 --- /dev/null +++ b/include/linux/flex_proportions.h @@ -0,0 +1,101 @@ +/* + * Floating proportions with flexible aging period + * + * Copyright (C) 2011, SUSE, Jan Kara <jack@suse.cz> + */ + +#ifndef _LINUX_FLEX_PROPORTIONS_H +#define _LINUX_FLEX_PROPORTIONS_H + +#include <linux/percpu_counter.h> +#include <linux/spinlock.h> +#include <linux/seqlock.h> + +/* + * When maximum proportion of some event type is specified, this is the + * precision with which we allow limitting. Note that this creates an upper + * bound on the number of events per period like + * ULLONG_MAX >> FPROP_FRAC_SHIFT. + */ +#define FPROP_FRAC_SHIFT 10 +#define FPROP_FRAC_BASE (1UL << FPROP_FRAC_SHIFT) + +/* + * ---- Global proportion definitions ---- + */ +struct fprop_global { + /* Number of events in the current period */ + struct percpu_counter events; + /* Current period */ + unsigned int period; + /* Synchronization with period transitions */ + seqcount_t sequence; +}; + +int fprop_global_init(struct fprop_global *p); +void fprop_global_destroy(struct fprop_global *p); +bool fprop_new_period(struct fprop_global *p, int periods); + +/* + * ---- SINGLE ---- + */ +struct fprop_local_single { + /* the local events counter */ + unsigned long events; + /* Period in which we last updated events */ + unsigned int period; + raw_spinlock_t lock; /* Protect period and numerator */ +}; + +#define INIT_FPROP_LOCAL_SINGLE(name) \ +{ .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \ +} + +int fprop_local_init_single(struct fprop_local_single *pl); +void fprop_local_destroy_single(struct fprop_local_single *pl); +void __fprop_inc_single(struct fprop_global *p, struct fprop_local_single *pl); +void fprop_fraction_single(struct fprop_global *p, + struct fprop_local_single *pl, unsigned long *numerator, + unsigned long *denominator); + +static inline +void fprop_inc_single(struct fprop_global *p, struct fprop_local_single *pl) +{ + unsigned long flags; + + local_irq_save(flags); + __fprop_inc_single(p, pl); + local_irq_restore(flags); +} + +/* + * ---- PERCPU ---- + */ +struct fprop_local_percpu { + /* the local events counter */ + struct percpu_counter events; + /* Period in which we last updated events */ + unsigned int period; + raw_spinlock_t lock; /* Protect period and numerator */ +}; + +int fprop_local_init_percpu(struct fprop_local_percpu *pl); +void fprop_local_destroy_percpu(struct fprop_local_percpu *pl); +void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl); +void __fprop_inc_percpu_max(struct fprop_global *p, struct fprop_local_percpu *pl, + int max_frac); +void fprop_fraction_percpu(struct fprop_global *p, + struct fprop_local_percpu *pl, unsigned long *numerator, + unsigned long *denominator); + +static inline +void fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl) +{ + unsigned long flags; + + local_irq_save(flags); + __fprop_inc_percpu(p, pl); + local_irq_restore(flags); +} + +#endif diff --git a/lib/Makefile b/lib/Makefile index 9cb4104f47d..42d283edc4d 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -11,7 +11,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \ rbtree.o radix-tree.o dump_stack.o timerqueue.o\ idr.o int_sqrt.o extable.o prio_tree.o \ sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \ - proportions.o prio_heap.o ratelimit.o show_mem.o \ + proportions.o flex_proportions.o prio_heap.o ratelimit.o show_mem.o \ is_single_threaded.o plist.o decompress.o lib-$(CONFIG_MMU) += ioremap.o diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c new file mode 100644 index 00000000000..c785554f952 --- /dev/null +++ b/lib/flex_proportions.c @@ -0,0 +1,272 @@ +/* + * Floating proportions with flexible aging period + * + * Copyright (C) 2011, SUSE, Jan Kara <jack@suse.cz> + * + * The goal of this code is: Given different types of event, measure proportion + * of each type of event over time. The proportions are measured with + * exponentially decaying history to give smooth transitions. A formula + * expressing proportion of event of type 'j' is: + * + * p_{j} = (\Sum_{i>=0} x_{i,j}/2^{i+1})/(\Sum_{i>=0} x_i/2^{i+1}) + * + * Where x_{i,j} is j's number of events in i-th last time period and x_i is + * total number of events in i-th last time period. + * + * Note that p_{j}'s are normalised, i.e. + * + * \Sum_{j} p_{j} = 1, + * + * This formula can be straightforwardly computed by maintaing denominator + * (let's call it 'd') and for each event type its numerator (let's call it + * 'n_j'). When an event of type 'j' happens, we simply need to do: + * n_j++; d++; + * + * When a new period is declared, we could do: + * d /= 2 + * for each j + * n_j /= 2 + * + * To avoid iteration over all event types, we instead shift numerator of event + * j lazily when someone asks for a proportion of event j or when event j + * occurs. This can bit trivially implemented by remembering last period in + * which something happened with proportion of type j. + */ +#include <linux/flex_proportions.h> + +int fprop_global_init(struct fprop_global *p) +{ + int err; + + p->period = 0; + /* Use 1 to avoid dealing with periods with 0 events... */ + err = percpu_counter_init(&p->events, 1); + if (err) + return err; + seqcount_init(&p->sequence); + return 0; +} + +void fprop_global_destroy(struct fprop_global *p) +{ + percpu_counter_destroy(&p->events); +} + +/* + * Declare @periods new periods. It is upto the caller to make sure period + * transitions cannot happen in parallel. + * + * The function returns true if the proportions are still defined and false + * if aging zeroed out all events. This can be used to detect whether declaring + * further periods has any effect. + */ +bool fprop_new_period(struct fprop_global *p, int periods) +{ + u64 events; + unsigned long flags; + + local_irq_save(flags); + events = percpu_counter_sum(&p->events); + /* + * Don't do anything if there are no events. + */ + if (events <= 1) { + local_irq_restore(flags); + return false; + } + write_seqcount_begin(&p->sequence); + if (periods < 64) + events -= events >> periods; + /* Use addition to avoid losing events happening between sum and set */ + percpu_counter_add(&p->events, -events); + p->period += periods; + write_seqcount_end(&p->sequence); + local_irq_restore(flags); + + return true; +} + +/* + * ---- SINGLE ---- + */ + +int fprop_local_init_single(struct fprop_local_single *pl) +{ + pl->events = 0; + pl->period = 0; + raw_spin_lock_init(&pl->lock); + return 0; +} + +void fprop_local_destroy_single(struct fprop_local_single *pl) +{ +} + +static void fprop_reflect_period_single(struct fprop_global *p, + struct fprop_local_single *pl) +{ + unsigned int period = p->period; + unsigned long flags; + + /* Fast path - period didn't change */ + if (pl->period == period) + return; + raw_spin_lock_irqsave(&pl->lock, flags); + /* Someone updated pl->period while we were spinning? */ + if (pl->period >= period) { + raw_spin_unlock_irqrestore(&pl->lock, flags); + return; + } + /* Aging zeroed our fraction? */ + if (period - pl->period < BITS_PER_LONG) + pl->events >>= period - pl->period; + else + pl->events = 0; + pl->period = period; + raw_spin_unlock_irqrestore(&pl->lock, flags); +} + +/* Event of type pl happened */ +void __fprop_inc_single(struct fprop_global *p, struct fprop_local_single *pl) +{ + fprop_reflect_period_single(p, pl); + pl->events++; + percpu_counter_add(&p->events, 1); +} + +/* Return fraction of events of type pl */ +void fprop_fraction_single(struct fprop_global *p, + struct fprop_local_single *pl, + unsigned long *numerator, unsigned long *denominator) +{ + unsigned int seq; + s64 num, den; + + do { + seq = read_seqcount_begin(&p->sequence); + fprop_reflect_period_single(p, pl); + num = pl->events; + den = percpu_counter_read_positive(&p->events); + } while (read_seqcount_retry(&p->sequence, seq)); + + /* + * Make fraction <= 1 and denominator > 0 even in presence of percpu + * counter errors + */ + if (den <= num) { + if (num) + den = num; + else + den = 1; + } + *denominator = den; + *numerator = num; +} + +/* + * ---- PERCPU ---- + */ +#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids))) + +int fprop_local_init_percpu(struct fprop_local_percpu *pl) +{ + int err; + + err = percpu_counter_init(&pl->events, 0); + if (err) + return err; + pl->period = 0; + raw_spin_lock_init(&pl->lock); + return 0; +} + +void fprop_local_destroy_percpu(struct fprop_local_percpu *pl) +{ + percpu_counter_destroy(&pl->events); +} + +static void fprop_reflect_period_percpu(struct fprop_global *p, + struct fprop_local_percpu *pl) +{ + unsigned int period = p->period; + unsigned long flags; + + /* Fast path - period didn't change */ + if (pl->period == period) + return; + raw_spin_lock_irqsave(&pl->lock, flags); + /* Someone updated pl->period while we were spinning? */ + if (pl->period >= period) { + raw_spin_unlock_irqrestore(&pl->lock, flags); + return; + } + /* Aging zeroed our fraction? */ + if (period - pl->period < BITS_PER_LONG) { + s64 val = percpu_counter_read(&pl->events); + + if (val < (nr_cpu_ids * PROP_BATCH)) + val = percpu_counter_sum(&pl->events); + + __percpu_counter_add(&pl->events, + -val + (val >> (period-pl->period)), PROP_BATCH); + } else + percpu_counter_set(&pl->events, 0); + pl->period = period; + raw_spin_unlock_irqrestore(&pl->lock, flags); +} + +/* Event of type pl happened */ +void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl) +{ + fprop_reflect_period_percpu(p, pl); + __percpu_counter_add(&pl->events, 1, PROP_BATCH); + percpu_counter_add(&p->events, 1); +} + +void fprop_fraction_percpu(struct fprop_global *p, + struct fprop_local_percpu *pl, + unsigned long *numerator, unsigned long *denominator) +{ + unsigned int seq; + s64 num, den; + + do { + seq = read_seqcount_begin(&p->sequence); + fprop_reflect_period_percpu(p, pl); + num = percpu_counter_read_positive(&pl->events); + den = percpu_counter_read_positive(&p->events); + } while (read_seqcount_retry(&p->sequence, seq)); + + /* + * Make fraction <= 1 and denominator > 0 even in presence of percpu + * counter errors + */ + if (den <= num) { + if (num) + den = num; + else + den = 1; + } + *denominator = den; + *numerator = num; +} + +/* + * Like __fprop_inc_percpu() except that event is counted only if the given + * type has fraction smaller than @max_frac/FPROP_FRAC_BASE + */ +void __fprop_inc_percpu_max(struct fprop_global *p, + struct fprop_local_percpu *pl, int max_frac) +{ + if (unlikely(max_frac < FPROP_FRAC_BASE)) { + unsigned long numerator, denominator; + + fprop_fraction_percpu(p, pl, &numerator, &denominator); + if (numerator > + (((u64)denominator) * max_frac) >> FPROP_FRAC_SHIFT) + return; + } else + fprop_reflect_period_percpu(p, pl); + __percpu_counter_add(&pl->events, 1, PROP_BATCH); + percpu_counter_add(&p->events, 1); +} diff --git a/mm/backing-dev.c b/mm/backing-dev.c index dd8e2aafb07..3387aea1120 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -677,7 +677,7 @@ int bdi_init(struct backing_dev_info *bdi) bdi->min_ratio = 0; bdi->max_ratio = 100; - bdi->max_prop_frac = PROP_FRAC_BASE; + bdi->max_prop_frac = FPROP_FRAC_BASE; spin_lock_init(&bdi->wb_lock); INIT_LIST_HEAD(&bdi->bdi_list); INIT_LIST_HEAD(&bdi->work_list); @@ -700,7 +700,7 @@ int bdi_init(struct backing_dev_info *bdi) bdi->write_bandwidth = INIT_BW; bdi->avg_write_bandwidth = INIT_BW; - err = prop_local_init_percpu(&bdi->completions); + err = fprop_local_init_percpu(&bdi->completions); if (err) { err: @@ -744,7 +744,7 @@ void bdi_destroy(struct backing_dev_info *bdi) for (i = 0; i < NR_BDI_STAT_ITEMS; i++) percpu_counter_destroy(&bdi->bdi_stat[i]); - prop_local_destroy_percpu(&bdi->completions); + fprop_local_destroy_percpu(&bdi->completions); } EXPORT_SYMBOL(bdi_destroy); diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 93d8d2f7108..e5363f34e02 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); } /** |