Check for background thread inactivity on extents_dalloc.

To avoid background threads sleeping forever with idle arenas, we eagerly check
background threads' sleep time after extents_dalloc, and signal the thread if
necessary.

2 files changed, 45 insertions, 4 deletions

diff --git a/include/jemalloc/internal/background_thread_inlines.h b/include/jemalloc/internal/background_thread_inlines.h
index 2709ae31..fd5095f2 100644
--- a/include/jemalloc/internal/background_thread_inlines.h
+++ b/include/jemalloc/internal/background_thread_inlines.h
@@ -18,4 +18,39 @@ arena_background_thread_info_get(arena_t *arena) {
 	return &background_thread_info[arena_ind % ncpus];
 }
 
+JEMALLOC_ALWAYS_INLINE uint64_t
+background_thread_wakeup_time_get(background_thread_info_t *info) {
+	uint64_t next_wakeup = nstime_ns(&info->next_wakeup);
+	assert(atomic_load_b(&info->indefinite_sleep, ATOMIC_ACQUIRE) ==
+	    (next_wakeup == BACKGROUND_THREAD_INDEFINITE_SLEEP));
+	return next_wakeup;
+}
+
+JEMALLOC_ALWAYS_INLINE void
+background_thread_wakeup_time_set(tsdn_t *tsdn, background_thread_info_t *info,
+    uint64_t wakeup_time) {
+	malloc_mutex_assert_owner(tsdn, &info->mtx);
+	atomic_store_b(&info->indefinite_sleep,
+	    wakeup_time == BACKGROUND_THREAD_INDEFINITE_SLEEP, ATOMIC_RELEASE);
+	nstime_init(&info->next_wakeup, wakeup_time);
+}
+
+JEMALLOC_ALWAYS_INLINE bool
+background_thread_indefinite_sleep(background_thread_info_t *info) {
+	return atomic_load_b(&info->indefinite_sleep, ATOMIC_ACQUIRE);
+}
+
+JEMALLOC_ALWAYS_INLINE void
+arena_background_thread_inactivity_check(tsdn_t *tsdn, arena_t *arena) {
+	if (!background_thread_enabled()) {
+		return;
+	}
+	background_thread_info_t *info =
+	    arena_background_thread_info_get(arena);
+	if (background_thread_indefinite_sleep(info)) {
+		background_thread_interval_check(tsdn, arena,
+		    &arena->decay_dirty, 0);
+	}
+}
+
 #endif /* JEMALLOC_INTERNAL_BACKGROUND_THREAD_INLINES_H */
diff --git a/include/jemalloc/internal/background_thread_structs.h b/include/jemalloc/internal/background_thread_structs.h
index c4eb8273..9507abcd 100644
--- a/include/jemalloc/internal/background_thread_structs.h
+++ b/include/jemalloc/internal/background_thread_structs.h
@@ -1,15 +1,22 @@
 #ifndef JEMALLOC_INTERNAL_BACKGROUND_THREAD_STRUCTS_H
 #define JEMALLOC_INTERNAL_BACKGROUND_THREAD_STRUCTS_H
 
+/* This file really combines "structs" and "types", but only transitionally. */
+
+#define BACKGROUND_THREAD_INDEFINITE_SLEEP UINT64_MAX
+
 struct background_thread_info_s {
-	malloc_mutex_t		mtx;
 #ifdef JEMALLOC_BACKGROUND_THREAD
 	/* Background thread is pthread specific. */
-	pthread_cond_t		cond;
 	pthread_t		thread;
+	pthread_cond_t		cond;
+#endif
+	malloc_mutex_t		mtx;
 	/* Whether the thread has been created. */
 	bool			started;
-	/* Next scheduled wakeup time (absolute time). */
+	/* When true, it means no wakeup scheduled. */
+	atomic_b_t		indefinite_sleep;
+	/* Next scheduled wakeup time (absolute time in ns). */
 	nstime_t		next_wakeup;
 	/*
 	 *  Since the last background thread run, newly added number of pages
@@ -22,7 +29,6 @@ struct background_thread_info_s {
 	uint64_t		tot_n_runs;
 	/* Stats: total sleep time since started. */
 	nstime_t		tot_sleep_time;
-#endif /* ifdef JEMALLOC_BACKGROUND_THREAD */
 };
 typedef struct background_thread_info_s background_thread_info_t;