Add a batch allocation interface to the PAI.

For now, no real allocator actually implements this interface; this will change
in subsequent diffs.

src/hpa.c

@@ -90,6 +90,7 @@ hpa_shard_init(hpa_shard_t *shard, emap_t *emap, base_t *base,
 	 * operating on corrupted data.
 	 */
 	shard->pai.alloc = &hpa_alloc;
+	shard->pai.alloc_batch = &pai_alloc_batch_default;
 	shard->pai.expand = &hpa_expand;
 	shard->pai.shrink = &hpa_shrink;
 	shard->pai.dalloc = &hpa_dalloc;

src/pac.c

@@ -91,6 +91,7 @@ pac_init(tsdn_t *tsdn, pac_t *pac, base_t *base, emap_t *emap,
 	atomic_store_zu(&pac->extent_sn_next, 0, ATOMIC_RELAXED);
 
 	pac->pai.alloc = &pac_alloc_impl;
+	pac->pai.alloc_batch = &pai_alloc_batch_default;
 	pac->pai.expand = &pac_expand_impl;
 	pac->pai.shrink = &pac_shrink_impl;
 	pac->pai.dalloc = &pac_dalloc_impl;

src/pai.c

@@ -1,6 +1,19 @@
 #include "jemalloc/internal/jemalloc_preamble.h"
 #include "jemalloc/internal/jemalloc_internal_includes.h"
 
+size_t
+pai_alloc_batch_default(tsdn_t *tsdn, pai_t *self, size_t size,
+    size_t nallocs, edata_list_active_t *results) {
+	for (size_t i = 0; i < nallocs; i++) {
+		edata_t *edata = pai_alloc(tsdn, self, size, PAGE,
+		    /* zero */ false);
+		if (edata == NULL) {
+			return i;
+		}
+		edata_list_active_append(results, edata);
+	}
+	return nallocs;
+}
 
 void
 pai_dalloc_batch_default(tsdn_t *tsdn, pai_t *self,

src/sec.c

@@ -52,6 +52,7 @@ sec_init(sec_t *sec, pai_t *fallback, size_t nshards, size_t alloc_max,
 	 * initialization failed will segfault in an easy-to-spot way.
 	 */
 	sec->pai.alloc = &sec_alloc;
+	sec->pai.alloc_batch = &pai_alloc_batch_default;
 	sec->pai.expand = &sec_expand;
 	sec->pai.shrink = &sec_shrink;
 	sec->pai.dalloc = &sec_dalloc;