--- /dev/null
+/*
+ * 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
--- /dev/null
+/*
+ * 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 = percpu_counter_sum(&p->events);
+
+ /*
+ * Don't do anything if there are no events.
+ */
+ if (events <= 1)
+ 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);
+
+ 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);
+}
projects / platform / upstream / kernel-adaptation-pc.git / commitdiff