Add HPA deferral functionality.

include/jemalloc/internal/arena_externs.h

@@ -51,6 +51,7 @@ bool arena_decay_ms_set(tsdn_t *tsdn, arena_t *arena, extent_state_t state,
 ssize_t arena_decay_ms_get(arena_t *arena, extent_state_t state);
 void arena_decay(tsdn_t *tsdn, arena_t *arena, bool is_background_thread,
     bool all);
+void arena_do_deferred_work(tsdn_t *tsdn, arena_t *arena);
 void arena_reset(tsd_t *tsd, arena_t *arena);
 void arena_destroy(tsd_t *tsd, arena_t *arena);
 void arena_cache_bin_fill_small(tsdn_t *tsdn, arena_t *arena,

include/jemalloc/internal/hpa.h

@@ -55,6 +55,7 @@ struct hpa_shard_s {
 	malloc_mutex_t mtx;
 	/* The base metadata allocator. */
 	base_t *base;
+
 	/*
 	 * This edata cache is the one we use when allocating a small extent
 	 * from a pageslab.  The pageslab itself comes from the centralized
@@ -122,6 +123,10 @@ void hpa_shard_stats_merge(tsdn_t *tsdn, hpa_shard_t *shard,
 void hpa_shard_disable(tsdn_t *tsdn, hpa_shard_t *shard);
 void hpa_shard_destroy(tsdn_t *tsdn, hpa_shard_t *shard);
 
+void hpa_shard_set_deferral_allowed(tsdn_t *tsdn, hpa_shard_t *shard,
+    bool deferral_allowed);
+void hpa_shard_do_deferred_work(tsdn_t *tsdn, hpa_shard_t *shard);
+
 /*
  * We share the fork ordering with the PA and arena prefork handling; that's why
  * these are 3 and 4 rather than 0 and 1.

include/jemalloc/internal/hpa_opts.h

@@ -32,6 +32,14 @@ struct hpa_shard_opts_s {
 	 * active_pages.  This may be set to (fxp_t)-1 to disable purging.
 	 */
 	fxp_t dirty_mult;
+
+	/*
+	 * Whether or not the PAI methods are allowed to defer work to a
+	 * subsequent hpa_shard_do_deferred_work() call.  Practically, this
+	 * corresponds to background threads being enabled.  We track this
+	 * ourselves for encapsulation purposes.
+	 */
+	bool deferral_allowed;
 };
 
 #define HPA_SHARD_OPTS_DEFAULT {					\
@@ -42,7 +50,15 @@ struct hpa_shard_opts_s {
 	/* dehugification_threshold */					\
 	HUGEPAGE * 20 / 100,						\
 	/* dirty_mult */						\
-	FXP_INIT_PERCENT(25)						\
+	FXP_INIT_PERCENT(25),						\
+	/*								\
+	 * deferral_allowed						\
+	 * 								\
+	 * Really, this is always set by the arena during creation	\
+	 * or by an hpa_shard_set_deferral_allowed call, so the value	\
+	 * we put here doesn't matter.					\
+	 */								\
+	false								\
 }
 
 #endif /* JEMALLOC_INTERNAL_HPA_OPTS_H */