1 files changed, 186 insertions, 0 deletions
diff --git a/deps/jemalloc/include/jemalloc/internal/decay.h b/deps/jemalloc/include/jemalloc/internal/decay.h
new file mode 100644
index 0000000..cf6a9d2
--- /dev/null
+++ b/deps/jemalloc/include/jemalloc/internal/decay.h
@@ -0,0 +1,186 @@
+#ifndef JEMALLOC_INTERNAL_DECAY_H
+#define JEMALLOC_INTERNAL_DECAY_H
+
+#include "jemalloc/internal/smoothstep.h"
+
+#define DECAY_UNBOUNDED_TIME_TO_PURGE ((uint64_t)-1)
+
+/*
+ * The decay_t computes the number of pages we should purge at any given time.
+ * Page allocators inform a decay object when pages enter a decay-able state
+ * (i.e. dirty or muzzy), and query it to determine how many pages should be
+ * purged at any given time.
+ *
+ * This is mostly a single-threaded data structure and doesn't care about
+ * synchronization at all; it's the caller's responsibility to manage their
+ * synchronization on their own.  There are two exceptions:
+ * 1) It's OK to racily call decay_ms_read (i.e. just the simplest state query).
+ * 2) The mtx and purging fields live (and are initialized) here, but are
+ *    logically owned by the page allocator.  This is just a convenience (since
+ *    those fields would be duplicated for both the dirty and muzzy states
+ *    otherwise).
+ */
+typedef struct decay_s decay_t;
+struct decay_s {
+	/* Synchronizes all non-atomic fields. */
+	malloc_mutex_t mtx;
+	/*
+	 * True if a thread is currently purging the extents associated with
+	 * this decay structure.
+	 */
+	bool purging;
+	/*
+	 * Approximate time in milliseconds from the creation of a set of unused
+	 * dirty pages until an equivalent set of unused dirty pages is purged
+	 * and/or reused.
+	 */
+	atomic_zd_t time_ms;
+	/* time / SMOOTHSTEP_NSTEPS. */
+	nstime_t interval;
+	/*
+	 * Time at which the current decay interval logically started.  We do
+	 * not actually advance to a new epoch until sometime after it starts
+	 * because of scheduling and computation delays, and it is even possible
+	 * to completely skip epochs.  In all cases, during epoch advancement we
+	 * merge all relevant activity into the most recently recorded epoch.
+	 */
+	nstime_t epoch;
+	/* Deadline randomness generator. */
+	uint64_t jitter_state;
+	/*
+	 * Deadline for current epoch.  This is the sum of interval and per
+	 * epoch jitter which is a uniform random variable in [0..interval).
+	 * Epochs always advance by precise multiples of interval, but we
+	 * randomize the deadline to reduce the likelihood of arenas purging in
+	 * lockstep.
+	 */
+	nstime_t deadline;
+	/*
+	 * The number of pages we cap ourselves at in the current epoch, per
+	 * decay policies.  Updated on an epoch change.  After an epoch change,
+	 * the caller should take steps to try to purge down to this amount.
+	 */
+	size_t npages_limit;
+	/*
+	 * Number of unpurged pages at beginning of current epoch.  During epoch
+	 * advancement we use the delta between arena->decay_*.nunpurged and
+	 * ecache_npages_get(&arena->ecache_*) to determine how many dirty pages,
+	 * if any, were generated.
+	 */
+	size_t nunpurged;
+	/*
+	 * Trailing log of how many unused dirty pages were generated during
+	 * each of the past SMOOTHSTEP_NSTEPS decay epochs, where the last
+	 * element is the most recent epoch.  Corresponding epoch times are
+	 * relative to epoch.
+	 *
+	 * Updated only on epoch advance, triggered by
+	 * decay_maybe_advance_epoch, below.
+	 */
+	size_t backlog[SMOOTHSTEP_NSTEPS];
+
+	/* Peak number of pages in associated extents.  Used for debug only. */
+	uint64_t ceil_npages;
+};
+
+/*
+ * The current decay time setting.  This is the only public access to a decay_t
+ * that's allowed without holding mtx.
+ */
+static inline ssize_t
+decay_ms_read(const decay_t *decay) {
+	return atomic_load_zd(&decay->time_ms, ATOMIC_RELAXED);
+}
+
+/*
+ * See the comment on the struct field -- the limit on pages we should allow in
+ * this decay state this epoch.
+ */
+static inline size_t
+decay_npages_limit_get(const decay_t *decay) {
+	return decay->npages_limit;
+}
+
+/* How many unused dirty pages were generated during the last epoch. */
+static inline size_t
+decay_epoch_npages_delta(const decay_t *decay) {
+	return decay->backlog[SMOOTHSTEP_NSTEPS - 1];
+}
+
+/*
+ * Current epoch duration, in nanoseconds.  Given that new epochs are started
+ * somewhat haphazardly, this is not necessarily exactly the time between any
+ * two calls to decay_maybe_advance_epoch; see the comments on fields in the
+ * decay_t.
+ */
+static inline uint64_t
+decay_epoch_duration_ns(const decay_t *decay) {
+	return nstime_ns(&decay->interval);
+}
+
+static inline bool
+decay_immediately(const decay_t *decay) {
+	ssize_t decay_ms = decay_ms_read(decay);
+	return decay_ms == 0;
+}
+
+static inline bool
+decay_disabled(const decay_t *decay) {
+	ssize_t decay_ms = decay_ms_read(decay);
+	return decay_ms < 0;
+}
+
+/* Returns true if decay is enabled and done gradually. */
+static inline bool
+decay_gradually(const decay_t *decay) {
+	ssize_t decay_ms = decay_ms_read(decay);
+	return decay_ms > 0;
+}
+
+/*
+ * Returns true if the passed in decay time setting is valid.
+ * < -1 : invalid
+ * -1   : never decay
+ *  0   : decay immediately
+ *  > 0 : some positive decay time, up to a maximum allowed value of
+ *  NSTIME_SEC_MAX * 1000, which corresponds to decaying somewhere in the early
+ *  27th century.  By that time, we expect to have implemented alternate purging
+ *  strategies.
+ */
+bool decay_ms_valid(ssize_t decay_ms);
+
+/*
+ * As a precondition, the decay_t must be zeroed out (as if with memset).
+ *
+ * Returns true on error.
+ */
+bool decay_init(decay_t *decay, nstime_t *cur_time, ssize_t decay_ms);
+
+/*
+ * Given an already-initialized decay_t, reinitialize it with the given decay
+ * time.  The decay_t must have previously been initialized (and should not then
+ * be zeroed).
+ */
+void decay_reinit(decay_t *decay, nstime_t *cur_time, ssize_t decay_ms);
+
+/*
+ * Compute how many of 'npages_new' pages we would need to purge in 'time'.
+ */
+uint64_t decay_npages_purge_in(decay_t *decay, nstime_t *time,
+    size_t npages_new);
+
+/* Returns true if the epoch advanced and there are pages to purge. */
+bool decay_maybe_advance_epoch(decay_t *decay, nstime_t *new_time,
+    size_t current_npages);
+
+/*
+ * Calculates wait time until a number of pages in the interval
+ * [0.5 * npages_threshold .. 1.5 * npages_threshold] should be purged.
+ *
+ * Returns number of nanoseconds or DECAY_UNBOUNDED_TIME_TO_PURGE in case of
+ * indefinite wait.
+ */
+uint64_t decay_ns_until_purge(decay_t *decay, size_t npages_current,
+    uint64_t npages_threshold);
+
+#endif /* JEMALLOC_INTERNAL_DECAY_H */