[master] add zone memory context pools

3492.	[bug]		Fixed a regression in zone loading performance
			due to lock contention. [RT #30399]

CHANGES

+3492.	[bug]		Fixed a regression in zone loading performance
+			due to lock contention. [RT #30399]
+
 3491.	[bug]		Slave zones using inline-signing must specify a
 			file name. [RT #31946]
 

bin/named/server.c

@@ -3028,7 +3028,8 @@ configure_view(dns_view_t *view, cfg_obj_t *config, cfg_obj_t *vconfig,
 				}
 			}
 
-			CHECK(dns_zone_create(&zone, mctx));
+			CHECK(dns_zonemgr_createzone(ns_g_server->zonemgr,
+						     &zone));
 			CHECK(dns_zone_setorigin(zone, name));
 			dns_zone_setview(zone, view);
 			CHECK(dns_zonemgr_managezone(ns_g_server->zonemgr,
@@ -3582,7 +3583,8 @@ configure_zone(const cfg_obj_t *config, const cfg_obj_t *zconfig,
 			dns_zone_attach(pview->redirect, &zone);
 			dns_zone_setview(zone, view);
 		} else {
-			CHECK(dns_zone_create(&zone, mctx));
+			CHECK(dns_zonemgr_createzone(ns_g_server->zonemgr,
+						     &zone));
 			CHECK(dns_zone_setorigin(zone, origin));
 			dns_zone_setview(zone, view);
 			CHECK(dns_zonemgr_managezone(ns_g_server->zonemgr,
@@ -3645,7 +3647,7 @@ configure_zone(const cfg_obj_t *config, const cfg_obj_t *zconfig,
 		 * We cannot reuse an existing zone, we have
 		 * to create a new one.
 		 */
-		CHECK(dns_zone_create(&zone, mctx));
+		CHECK(dns_zonemgr_createzone(ns_g_server->zonemgr, &zone));
 		CHECK(dns_zone_setorigin(zone, origin));
 		dns_zone_setview(zone, view);
 		if (view->acache != NULL)
@@ -3763,7 +3765,7 @@ add_keydata_zone(dns_view_t *view, const char *directory, isc_mem_t *mctx) {
 	}
 
 	/* No existing keydata zone was found; create one */
-	CHECK(dns_zone_create(&zone, mctx));
+	CHECK(dns_zonemgr_createzone(ns_g_server->zonemgr, &zone));
 	CHECK(dns_zone_setorigin(zone, dns_rootname));
 
 	isc_sha256_data((void *)view->name, strlen(view->name), buffer);

bin/named/xfrout.c

@@ -247,7 +247,8 @@ ixfr_rrstream_create(isc_mem_t *mctx,
 	s = isc_mem_get(mctx, sizeof(*s));
 	if (s == NULL)
 		return (ISC_R_NOMEMORY);
-	s->common.mctx = mctx;
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
 	s->common.methods = &ixfr_rrstream_methods;
 	s->journal = NULL;
 
@@ -289,7 +290,7 @@ ixfr_rrstream_destroy(rrstream_t **rsp) {
 	ixfr_rrstream_t *s = (ixfr_rrstream_t *) *rsp;
 	if (s->journal != 0)
 		dns_journal_destroy(&s->journal);
-	isc_mem_put(s->common.mctx, s, sizeof(*s));
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
 }
 
 static rrstream_methods_t ixfr_rrstream_methods = {
@@ -335,7 +336,8 @@ axfr_rrstream_create(isc_mem_t *mctx, dns_db_t *db, dns_dbversion_t *ver,
 	s = isc_mem_get(mctx, sizeof(*s));
 	if (s == NULL)
 		return (ISC_R_NOMEMORY);
-	s->common.mctx = mctx;
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
 	s->common.methods = &axfr_rrstream_methods;
 	s->it_valid = ISC_FALSE;
 
@@ -413,7 +415,7 @@ axfr_rrstream_destroy(rrstream_t **rsp) {
 	axfr_rrstream_t *s = (axfr_rrstream_t *) *rsp;
 	if (s->it_valid)
 		dns_rriterator_destroy(&s->it);
-	isc_mem_put(s->common.mctx, s, sizeof(*s));
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
 }
 
 static rrstream_methods_t axfr_rrstream_methods = {
@@ -455,7 +457,8 @@ soa_rrstream_create(isc_mem_t *mctx, dns_db_t *db, dns_dbversion_t *ver,
 	s = isc_mem_get(mctx, sizeof(*s));
 	if (s == NULL)
 		return (ISC_R_NOMEMORY);
-	s->common.mctx = mctx;
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
 	s->common.methods = &soa_rrstream_methods;
 	s->soa_tuple = NULL;
 
@@ -497,7 +500,7 @@ soa_rrstream_destroy(rrstream_t **rsp) {
 	soa_rrstream_t *s = (soa_rrstream_t *) *rsp;
 	if (s->soa_tuple != NULL)
 		dns_difftuple_free(&s->soa_tuple);
-	isc_mem_put(s->common.mctx, s, sizeof(*s));
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
 }
 
 static rrstream_methods_t soa_rrstream_methods = {
@@ -561,7 +564,8 @@ compound_rrstream_create(isc_mem_t *mctx, rrstream_t **soa_stream,
 	s = isc_mem_get(mctx, sizeof(*s));
 	if (s == NULL)
 		return (ISC_R_NOMEMORY);
-	s->common.mctx = mctx;
+	s->common.mctx = NULL;
+	isc_mem_attach(mctx, &s->common.mctx);
 	s->common.methods = &compound_rrstream_methods;
 	s->components[0] = *soa_stream;
 	s->components[1] = *data_stream;
@@ -634,7 +638,7 @@ compound_rrstream_destroy(rrstream_t **rsp) {
 	s->components[0]->methods->destroy(&s->components[0]);
 	s->components[1]->methods->destroy(&s->components[1]);
 	s->components[2] = NULL; /* Copy of components[0]. */
-	isc_mem_put(s->common.mctx, s, sizeof(*s));
+	isc_mem_putanddetach(&s->common.mctx, s, sizeof(*s));
 }
 
 static rrstream_methods_t compound_rrstream_methods = {

lib/dns/acl.c

@@ -48,7 +48,10 @@ dns_acl_create(isc_mem_t *mctx, int n, dns_acl_t **target) {
 	acl = isc_mem_get(mctx, sizeof(*acl));
 	if (acl == NULL)
 		return (ISC_R_NOMEMORY);
-	acl->mctx = mctx;
+
+	acl->mctx = NULL;
+	isc_mem_attach(mctx, &acl->mctx);
+
 	acl->name = NULL;
 
 	result = isc_refcount_init(&acl->refcount, 1);
@@ -467,7 +470,7 @@ destroy(dns_acl_t *dacl) {
 		dns_iptable_detach(&dacl->iptable);
 	isc_refcount_destroy(&dacl->refcount);
 	dacl->magic = 0;
-	isc_mem_put(dacl->mctx, dacl, sizeof(*dacl));
+	isc_mem_putanddetach(&dacl->mctx, dacl, sizeof(*dacl));
 }
 
 void

lib/dns/byaddr.c

@@ -224,7 +224,8 @@ dns_byaddr_create(isc_mem_t *mctx, isc_netaddr_t *address, dns_view_t *view,
 	byaddr = isc_mem_get(mctx, sizeof(*byaddr));
 	if (byaddr == NULL)
 		return (ISC_R_NOMEMORY);
-	byaddr->mctx = mctx;
+	byaddr->mctx = NULL;
+	isc_mem_attach(mctx, &byaddr->mctx);
 	byaddr->options = options;
 
 	byaddr->event = isc_mem_get(mctx, sizeof(*byaddr->event));
@@ -277,7 +278,7 @@ dns_byaddr_create(isc_mem_t *mctx, isc_netaddr_t *address, dns_view_t *view,
 	isc_task_detach(&byaddr->task);
 
  cleanup_byaddr:
-	isc_mem_put(mctx, byaddr, sizeof(*byaddr));
+	isc_mem_putanddetach(&mctx, byaddr, sizeof(*byaddr));
 
 	return (result);
 }
@@ -310,7 +311,7 @@ dns_byaddr_destroy(dns_byaddr_t **byaddrp) {
 
 	DESTROYLOCK(&byaddr->lock);
 	byaddr->magic = 0;
-	isc_mem_put(byaddr->mctx, byaddr, sizeof(*byaddr));
+	isc_mem_putanddetach(&byaddr->mctx, byaddr, sizeof(*byaddr));
 
 	*byaddrp = NULL;
 }

lib/dns/dbtable.c

@@ -89,7 +89,8 @@ dns_dbtable_create(isc_mem_t *mctx, dns_rdataclass_t rdclass,
 		goto clean3;
 
 	dbtable->default_db = NULL;
-	dbtable->mctx = mctx;
+	dbtable->mctx = NULL;
+	isc_mem_attach(mctx, &dbtable->mctx);
 	dbtable->rdclass = rdclass;
 	dbtable->magic = DBTABLE_MAGIC;
 	dbtable->references = 1;
@@ -105,7 +106,7 @@ dns_dbtable_create(isc_mem_t *mctx, dns_rdataclass_t rdclass,
 	dns_rbt_destroy(&dbtable->rbt);
 
  clean1:
-	isc_mem_put(mctx, dbtable, sizeof(*dbtable));
+	isc_mem_putanddetach(&mctx, dbtable, sizeof(*dbtable));
 
 	return (result);
 }
@@ -129,7 +130,7 @@ dbtable_free(dns_dbtable_t *dbtable) {
 
 	dbtable->magic = 0;
 
-	isc_mem_put(dbtable->mctx, dbtable, sizeof(*dbtable));
+	isc_mem_putanddetach(&dbtable->mctx, dbtable, sizeof(*dbtable));
 }
 
 void

lib/dns/diff.c

@@ -73,7 +73,8 @@ dns_difftuple_create(isc_mem_t *mctx,
 	t = isc_mem_allocate(mctx, size);
 	if (t == NULL)
 		return (ISC_R_NOMEMORY);
-	t->mctx = mctx;
+	t->mctx = NULL;
+	isc_mem_attach(mctx, &t->mctx);
 	t->op = op;
 
 	datap = (unsigned char *)(t + 1);
@@ -105,10 +106,15 @@ dns_difftuple_create(isc_mem_t *mctx,
 void
 dns_difftuple_free(dns_difftuple_t **tp) {
 	dns_difftuple_t *t = *tp;
+	isc_mem_t *mctx;
+
 	REQUIRE(DNS_DIFFTUPLE_VALID(t));
+
 	dns_name_invalidate(&t->name);
 	t->magic = 0;
-	isc_mem_free(t->mctx, t);
+	mctx = t->mctx;
+	isc_mem_free(mctx, t);
+	isc_mem_detach(&mctx);
 	*tp = NULL;
 }
 

lib/dns/dst_api.c

@@ -1149,7 +1149,7 @@ dst_key_free(dst_key_t **keyp) {
 		isc_buffer_free(&key->key_tkeytoken);
 	}
 	memset(key, 0, sizeof(dst_key_t));
-	isc_mem_put(mctx, key, sizeof(dst_key_t));
+	isc_mem_putanddetach(&mctx, key, sizeof(dst_key_t));
 	*keyp = NULL;
 }
 
@@ -1348,10 +1348,10 @@ get_key_struct(dns_name_t *name, unsigned int alg,
 		isc_mem_put(mctx, key, sizeof(dst_key_t));
 		return (NULL);
 	}
+	isc_mem_attach(mctx, &key->mctx);
 	key->key_alg = alg;
 	key->key_flags = flags;
 	key->key_proto = protocol;
-	key->mctx = mctx;
 	key->keydata.generic = NULL;
 	key->key_size = bits;
 	key->key_class = rdclass;

lib/dns/include/dns/zone.h

@@ -1440,6 +1440,18 @@ dns_zonemgr_setsize(dns_zonemgr_t *zmgr, int num_zones);
  *\li	zmgr->zonetasks has been initialized.
  */
 
+isc_result_t
+dns_zonemgr_createzone(dns_zonemgr_t *zmgr, dns_zone_t **zonep);
+/*%<
+ *	Allocate a new zone using a memory context from the
+ *	zone manager's memory context pool.
+ *
+ * Require:
+ *\li	'zmgr' to be a valid zone manager.
+ *\li	'zonep' != NULL and '*zonep' == NULL.
+ */
+
+
 isc_result_t
 dns_zonemgr_managezone(dns_zonemgr_t *zmgr, dns_zone_t *zone);
 /*%<

lib/dns/iptable.c

@@ -36,7 +36,8 @@ dns_iptable_create(isc_mem_t *mctx, dns_iptable_t **target) {
 	tab = isc_mem_get(mctx, sizeof(*tab));
 	if (tab == NULL)
 		return (ISC_R_NOMEMORY);
-	tab->mctx = mctx;
+	tab->mctx = NULL;
+	isc_mem_attach(mctx, &tab->mctx);
 	isc_refcount_init(&tab->refcount, 1);
 	tab->radix = NULL;
 	tab->magic = DNS_IPTABLE_MAGIC;
@@ -184,5 +185,5 @@ destroy_iptable(dns_iptable_t *dtab) {
 
 	isc_refcount_destroy(&dtab->refcount);
 	dtab->magic = 0;
-	isc_mem_put(dtab->mctx, dtab, sizeof(*dtab));
+	isc_mem_putanddetach(&dtab->mctx, dtab, sizeof(*dtab));
 }

lib/dns/journal.c

@@ -568,7 +568,8 @@ journal_open(isc_mem_t *mctx, const char *filename, isc_boolean_t write,
 	if (j == NULL)
 		return (ISC_R_NOMEMORY);
 
-	j->mctx = mctx;
+	j->mctx = NULL;
+	isc_mem_attach(mctx, &j->mctx);
 	j->state = JOURNAL_STATE_INVALID;
 	j->fp = NULL;
 	j->filename = filename;
@@ -679,7 +680,7 @@ journal_open(isc_mem_t *mctx, const char *filename, isc_boolean_t write,
 	}
 	if (j->fp != NULL)
 		(void)isc_stdio_close(j->fp);
-	isc_mem_put(j->mctx, j, sizeof(*j));
+	isc_mem_putanddetach(&j->mctx, j, sizeof(*j));
 	return (result);
 }
 
@@ -1244,7 +1245,7 @@ dns_journal_destroy(dns_journal_t **journalp) {
 	if (j->fp != NULL)
 		(void)isc_stdio_close(j->fp);
 	j->magic = 0;
-	isc_mem_put(j->mctx, j, sizeof(*j));
+	isc_mem_putanddetach(&j->mctx, j, sizeof(*j));
 	*journalp = NULL;
 }
 

lib/dns/keytable.c

@@ -67,7 +67,8 @@ dns_keytable_create(isc_mem_t *mctx, dns_keytable_t **keytablep) {
 	if (result != ISC_R_SUCCESS)
 		goto cleanup_lock;
 
-	keytable->mctx = mctx;
+	keytable->mctx = NULL;
+	isc_mem_attach(mctx, &keytable->mctx);
 	keytable->active_nodes = 0;
 	keytable->references = 1;
 	keytable->magic = KEYTABLE_MAGIC;
@@ -82,7 +83,7 @@ dns_keytable_create(isc_mem_t *mctx, dns_keytable_t **keytablep) {
 	dns_rbt_destroy(&keytable->table);
 
    cleanup_keytable:
-	isc_mem_put(mctx, keytable, sizeof(*keytable));
+	isc_mem_putanddetach(&mctx, keytable, sizeof(*keytable));
 
 	return (result);
 }
@@ -137,7 +138,8 @@ dns_keytable_detach(dns_keytable_t **keytablep) {
 		isc_rwlock_destroy(&keytable->rwlock);
 		DESTROYLOCK(&keytable->lock);
 		keytable->magic = 0;
-		isc_mem_put(keytable->mctx, keytable, sizeof(*keytable));
+		isc_mem_putanddetach(&keytable->mctx,
+				     keytable, sizeof(*keytable));
 	}
 
 	*keytablep = NULL;

lib/dns/lookup.c

@@ -393,7 +393,8 @@ dns_lookup_create(isc_mem_t *mctx, dns_name_t *name, dns_rdatatype_t type,
 	lookup = isc_mem_get(mctx, sizeof(*lookup));
 	if (lookup == NULL)
 		return (ISC_R_NOMEMORY);
-	lookup->mctx = mctx;
+	lookup->mctx = NULL;
+	isc_mem_attach(mctx, &lookup->mctx);
 	lookup->options = options;
 
 	ievent = isc_event_allocate(mctx, lookup, DNS_EVENT_LOOKUPDONE,
@@ -452,7 +453,7 @@ dns_lookup_create(isc_mem_t *mctx, dns_name_t *name, dns_rdatatype_t type,
 	isc_task_detach(&lookup->task);
 
  cleanup_lookup:
-	isc_mem_put(mctx, lookup, sizeof(*lookup));
+	isc_mem_putanddetach(&mctx, lookup, sizeof(*lookup));
 
 	return (result);
 }
@@ -491,7 +492,7 @@ dns_lookup_destroy(dns_lookup_t **lookupp) {
 
 	DESTROYLOCK(&lookup->lock);
 	lookup->magic = 0;
-	isc_mem_put(lookup->mctx, lookup, sizeof(*lookup));
+	isc_mem_putanddetach(&lookup->mctx, lookup, sizeof(*lookup));
 
 	*lookupp = NULL;
 }

lib/dns/message.c

@@ -732,7 +732,9 @@ dns_message_create(isc_mem_t *mctx, unsigned int intent, dns_message_t **msgp)
 
 	for (i = 0; i < DNS_SECTION_MAX; i++)
 		ISC_LIST_INIT(m->sections[i]);
-	m->mctx = mctx;
+
+	m->mctx = NULL;
+	isc_mem_attach(mctx, &m->mctx);
 
 	ISC_LIST_INIT(m->scratchpad);
 	ISC_LIST_INIT(m->cleanup);
@@ -786,7 +788,7 @@ dns_message_create(isc_mem_t *mctx, unsigned int intent, dns_message_t **msgp)
 	if (m->rdspool != NULL)
 		isc_mempool_destroy(&m->rdspool);
 	m->magic = 0;
-	isc_mem_put(mctx, m, sizeof(dns_message_t));
+	isc_mem_putanddetach(&mctx, m, sizeof(dns_message_t));
 
 	return (ISC_R_NOMEMORY);
 }
@@ -815,7 +817,7 @@ dns_message_destroy(dns_message_t **msgp) {
 	isc_mempool_destroy(&msg->namepool);
 	isc_mempool_destroy(&msg->rdspool);
 	msg->magic = 0;
-	isc_mem_put(msg->mctx, msg, sizeof(dns_message_t));
+	isc_mem_putanddetach(&msg->mctx, msg, sizeof(dns_message_t));
 }
 
 static isc_result_t

lib/dns/rbt.c

@@ -755,7 +755,8 @@ dns_rbt_create(isc_mem_t *mctx, void (*deleter)(void *, void *),
 	if (rbt == NULL)
 		return (ISC_R_NOMEMORY);
 
-	rbt->mctx = mctx;
+	rbt->mctx = NULL;
+	isc_mem_attach(mctx, &rbt->mctx);
 	rbt->data_deleter = deleter;
 	rbt->deleter_arg = deleter_arg;
 	rbt->root = NULL;
@@ -767,7 +768,7 @@ dns_rbt_create(isc_mem_t *mctx, void (*deleter)(void *, void *),
 #ifdef DNS_RBT_USEHASH
 	result = inithash(rbt);
 	if (result != ISC_R_SUCCESS) {
-		isc_mem_put(mctx, rbt, sizeof(*rbt));
+		isc_mem_putanddetach(&rbt->mctx, rbt, sizeof(*rbt));
 		return (result);
 	}
 #endif
@@ -809,7 +810,7 @@ dns_rbt_destroy2(dns_rbt_t **rbtp, unsigned int quantum) {
 
 	rbt->magic = 0;
 
-	isc_mem_put(rbt->mctx, rbt, sizeof(*rbt));
+	isc_mem_putanddetach(&rbt->mctx, rbt, sizeof(*rbt));
 	*rbtp = NULL;
 	return (ISC_R_SUCCESS);
 }

lib/dns/tests/dnstest.c

@@ -212,7 +212,9 @@ dns_test_makezone(const char *name, dns_zone_t **zonep, dns_view_t *view,
 	else if (!keepview)
 		keepview = ISC_TRUE;
 
-	CHECK(dns_zone_create(&zone, mctx));
+	zone = *zonep;
+	if (zone == NULL)
+		CHECK(dns_zone_create(&zone, mctx));
 
 	isc_buffer_constinit(&buffer, name, strlen(name));
 	isc_buffer_add(&buffer, strlen(name));

lib/dns/tests/zonemgr_test.c

@@ -110,6 +110,46 @@ ATF_TC_BODY(zonemgr_managezone, tc) {
 	dns_test_end();
 }
 
+ATF_TC(zonemgr_createzone);
+ATF_TC_HEAD(zonemgr_createzone, tc) {
+	atf_tc_set_md_var(tc, "descr", "create and release a zone");
+}
+ATF_TC_BODY(zonemgr_createzone, tc) {
+	dns_zonemgr_t *zonemgr = NULL;
+	dns_zone_t *zone = NULL;
+	isc_result_t result;
+
+	UNUSED(tc);
+
+	result = dns_test_begin(NULL, ISC_TRUE);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+
+	result = dns_zonemgr_create(mctx, taskmgr, timermgr, socketmgr,
+				    &zonemgr);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+
+	/* This should not succeed until the dns_zonemgr_setsize() is run */
+	result = dns_zonemgr_createzone(zonemgr, &zone);
+	ATF_REQUIRE_EQ(result, ISC_R_FAILURE);
+
+	result = dns_zonemgr_setsize(zonemgr, 1);
+	ATF_REQUIRE_EQ(result, ISC_R_SUCCESS);
+
+	/* Now it should succeed */
+	result = dns_zonemgr_createzone(zonemgr, &zone);
+	ATF_CHECK_EQ(result, ISC_R_SUCCESS);
+	ATF_CHECK(zone != NULL);
+
+	if (zone != NULL)
+		dns_zone_detach(&zone);
+
+	dns_zonemgr_shutdown(zonemgr);
+	dns_zonemgr_detach(&zonemgr);
+	ATF_REQUIRE_EQ(zonemgr, NULL);
+
+	dns_test_end();
+}
+
 ATF_TC(zonemgr_unreachable);
 ATF_TC_HEAD(zonemgr_unreachable, tc) {
 	atf_tc_set_md_var(tc, "descr", "manage and release a zone");
@@ -182,6 +222,7 @@ ATF_TC_BODY(zonemgr_unreachable, tc) {
 ATF_TP_ADD_TCS(tp) {
 	ATF_TP_ADD_TC(tp, zonemgr_create);
 	ATF_TP_ADD_TC(tp, zonemgr_managezone);
+	ATF_TP_ADD_TC(tp, zonemgr_createzone);
 	ATF_TP_ADD_TC(tp, zonemgr_unreachable);
 	return (atf_no_error());
 }

lib/dns/win32/libdns.def

@@ -951,6 +951,7 @@ dns_zone_unload
 dns_zonekey_iszonekey
 dns_zonemgr_attach
 dns_zonemgr_create
+dns_zonemgr_createzone
 dns_zonemgr_detach
 dns_zonemgr_forcemaint
 dns_zonemgr_getcount

lib/dns/zone.c

@@ -25,6 +25,7 @@
 #include <isc/file.h>
 #include <isc/hex.h>
 #include <isc/mutex.h>
+#include <isc/pool.h>
 #include <isc/print.h>
 #include <isc/random.h>
 #include <isc/ratelimiter.h>
@@ -469,6 +470,7 @@ struct dns_zonemgr {
 	isc_taskpool_t *	zonetasks;
 	isc_taskpool_t *	loadtasks;
 	isc_task_t *		task;
+	isc_pool_t *		mctxpool;
 	isc_ratelimiter_t *	rl;
 	isc_rwlock_t		rwlock;
 	isc_mutex_t		iolock;
@@ -14004,6 +14006,7 @@ dns_zonemgr_create(isc_mem_t *mctx, isc_taskmgr_t *taskmgr,
 	zmgr->socketmgr = socketmgr;
 	zmgr->zonetasks = NULL;
 	zmgr->loadtasks = NULL;
+	zmgr->mctxpool = NULL;
 	zmgr->task = NULL;
 	zmgr->rl = NULL;
 	ISC_LIST_INIT(zmgr->zones);
@@ -14071,6 +14074,33 @@ dns_zonemgr_create(isc_mem_t *mctx, isc_taskmgr_t *taskmgr,
 	return (result);
 }
 
+isc_result_t
+dns_zonemgr_createzone(dns_zonemgr_t *zmgr, dns_zone_t **zonep) {
+	isc_result_t result;
+	isc_mem_t *mctx = NULL;
+	dns_zone_t *zone = NULL;
+	void *item;
+
+	REQUIRE(DNS_ZONEMGR_VALID(zmgr));
+	REQUIRE(zonep != NULL && *zonep == NULL);
+
+	if (zmgr->mctxpool == NULL)
+		return (ISC_R_FAILURE);
+
+	item = isc_pool_get(zmgr->mctxpool);
+	if (item == NULL)
+		return (ISC_R_FAILURE);
+
+	isc_mem_attach((isc_mem_t *) item, &mctx);
+	result = dns_zone_create(&zone, mctx);
+	isc_mem_detach(&mctx);
+
+	if (result == ISC_R_SUCCESS)
+		*zonep = zone;
+
+	return (result);
+}
+
 isc_result_t
 dns_zonemgr_managezone(dns_zonemgr_t *zmgr, dns_zone_t *zone) {
 	isc_result_t result;
@@ -14237,6 +14267,8 @@ dns_zonemgr_shutdown(dns_zonemgr_t *zmgr) {
 		isc_taskpool_destroy(&zmgr->zonetasks);
 	if (zmgr->loadtasks != NULL)
 		isc_taskpool_destroy(&zmgr->loadtasks);
+	if (zmgr->mctxpool != NULL)
+		isc_pool_destroy(&zmgr->mctxpool);
 
 	RWLOCK(&zmgr->rwlock, isc_rwlocktype_read);
 	for (zone = ISC_LIST_HEAD(zmgr->zones);
@@ -14250,21 +14282,54 @@ dns_zonemgr_shutdown(dns_zonemgr_t *zmgr) {
 	RWUNLOCK(&zmgr->rwlock, isc_rwlocktype_read);
 }
 
+static isc_result_t
+mctxinit(void **target, void *arg) {
+	isc_result_t result;
+	isc_mem_t *mctx = NULL;
+
+	UNUSED(arg);
+
+	REQUIRE(target != NULL && *target == NULL);
+
+	result = isc_mem_create(0, 0, &mctx);
+	if (result != ISC_R_SUCCESS)
+		return (result);
+	isc_mem_setname(mctx, "zonemgr-pool", NULL);
+
+	*target = mctx;
+	return (ISC_R_SUCCESS);
+}
+
+static void
+mctxfree(void **target) {
+	isc_mem_t *mctx = *(isc_mem_t **) target;
+	isc_mem_detach(&mctx);
+	*target = NULL;
+}
+
+#define ZONES_PER_TASK 100
+#define ZONES_PER_MCTX 1000
+
 isc_result_t
 dns_zonemgr_setsize(dns_zonemgr_t *zmgr, int num_zones) {
 	isc_result_t result;
-	int ntasks = num_zones / 100;
+	int ntasks = num_zones / ZONES_PER_TASK;
+	int nmctx = num_zones / ZONES_PER_MCTX;
 	isc_taskpool_t *pool = NULL;
+	isc_pool_t *mctxpool = NULL;
 
 	REQUIRE(DNS_ZONEMGR_VALID(zmgr));
 
 	/*
 	 * For anything fewer than 1000 zones we use 10 tasks in
 	 * the task pools.  More than that, and we'll scale at one
-	 * task per 100 zones.
+	 * task per 100 zones.  Similarly, for anything smaller than
+	 * 2000 zones we use 2 memory contexts, then scale at 1:1000.
 	 */
 	if (ntasks < 10)
 		ntasks = 10;
+	if (nmctx < 2)
+		nmctx = 2;
 
 	/* Create or resize the zone task pools. */