PAI/SEC: Add a dalloc_batch function.

This lets the SEC flush all of its items in a single call, rather than flushing
everything at once.

src/hpa.c

@@ -91,6 +91,7 @@ hpa_shard_init(hpa_shard_t *shard, emap_t *emap, base_t *base,
 	shard->pai.expand = &hpa_expand;
 	shard->pai.shrink = &hpa_shrink;
 	shard->pai.dalloc = &hpa_dalloc;
+	shard->pai.dalloc_batch = &pai_dalloc_batch_default;
 
 	return false;
 }

src/pac.c

@@ -94,6 +94,7 @@ pac_init(tsdn_t *tsdn, pac_t *pac, base_t *base, emap_t *emap,
 	pac->pai.expand = &pac_expand_impl;
 	pac->pai.shrink = &pac_shrink_impl;
 	pac->pai.dalloc = &pac_dalloc_impl;
+	pac->pai.dalloc_batch = &pai_dalloc_batch_default;
 
 	return false;
 }

src/pai.c

@@ -0,0 +1,13 @@
+#include "jemalloc/internal/jemalloc_preamble.h"
+#include "jemalloc/internal/jemalloc_internal_includes.h"
+
+
+void
+pai_dalloc_batch_default(tsdn_t *tsdn, pai_t *self,
+    edata_list_active_t *list) {
+	edata_t *edata;
+	while ((edata = edata_list_active_first(list)) != NULL) {
+		edata_list_active_remove(list, edata);
+		pai_dalloc(tsdn, self, edata);
+	}
+}

src/sec.c

@@ -46,6 +46,7 @@ bool sec_init(sec_t *sec, pai_t *fallback, size_t nshards, size_t alloc_max,
 	sec->pai.expand = &sec_expand;
 	sec->pai.shrink = &sec_shrink;
 	sec->pai.dalloc = &sec_dalloc;
+	sec->pai.dalloc_batch = &pai_dalloc_batch_default;
 
 	return false;
 }
@@ -142,6 +143,7 @@ sec_do_flush_locked(tsdn_t *tsdn, sec_t *sec, sec_shard_t *shard) {
 	for (pszind_t i = 0; i < SEC_NPSIZES; i++) {
 		edata_list_active_concat(&to_flush, &shard->freelist[i]);
 	}
+
 	/*
 	 * A better way to do this would be to add a batch dalloc function to
 	 * the pai_t.  Practically, the current method turns into O(n) locks and
@@ -149,11 +151,7 @@ sec_do_flush_locked(tsdn_t *tsdn, sec_t *sec, sec_shard_t *shard) {
 	 * HPA) can straightforwardly do many deallocations in a single lock /
 	 * unlock pair.
 	 */
-	while (!edata_list_active_empty(&to_flush)) {
-		edata_t *e = edata_list_active_first(&to_flush);
-		edata_list_active_remove(&to_flush, e);
-		pai_dalloc(tsdn, sec->fallback, e);
-	}
+	pai_dalloc_batch(tsdn, sec->fallback, &to_flush);
 }
 
 static void