From: Alessio Podda <alessio@isc.org>
Date: Mon, 3 Aug 2026 14:31:31 +0000 (+0200)
Subject: Align qpzone lock and db refcount
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=cbbc68566bb3fd66da6627229886fd58889ecd69;p=thirdparty%2Fbind9.git

Align qpzone lock and db refcount

The qpzone refcount is the probably the most conteded refcount for
workloads with a single zone such as TLDs.

Add alignment to both the refcount and qpzone dblock to avoid false
sharing.
---

diff --git a/lib/dns/qpzone.c b/lib/dns/qpzone.c
index 43de5890018..bf5f38633b9 100644
--- a/lib/dns/qpzone.c
+++ b/lib/dns/qpzone.c
@@ -214,7 +214,7 @@ struct qpzonedb {
 	/* Unlocked. */
 	dns_db_t common;
 	/* Locks the data in this struct */
-	isc_rwlock_t lock;
+	__attribute__((aligned(ISC_OS_CACHELINE_SIZE))) isc_rwlock_t lock;
 
 	/*
 	 * NOTE: 'references' is NOT the global reference counter for
@@ -579,7 +579,8 @@ free_db_rcu(struct rcu_head *rcu_head) {
 		INSIST(!cds_lfht_destroy(qpdb->common.update_listeners, NULL));
 	}
 
-	isc_mem_putanddetach(&qpdb->common.mctx, qpdb, sizeof(*qpdb));
+	isc_mem_putanddetachx(&qpdb->common.mctx, qpdb, sizeof(*qpdb),
+			      ISC_MEM_ALIGN(ISC_OS_CACHELINE_SIZE));
 }
 
 static void
@@ -863,7 +864,8 @@ dns__qpzone_create(isc_mem_t *mctx, const dns_name_t *origin, dns_dbtype_t type,
 	isc_result_t result;
 	dns_qp_t *qp = NULL;
 
-	qpdb = isc_mem_get(mctx, sizeof(*qpdb));
+	qpdb = isc_mem_getx(mctx, sizeof(*qpdb),
+			    ISC_MEM_ALIGN(ISC_OS_CACHELINE_SIZE));
 	*qpdb = (qpzonedb_t){
 		.common.origin = DNS_NAME_INITEMPTY,
 		.common.rdclass = rdclass,
diff --git a/tests/dns/qpzone_test.c b/tests/dns/qpzone_test.c
index 104ac15699d..315aec7866f 100644
--- a/tests/dns/qpzone_test.c
+++ b/tests/dns/qpzone_test.c
@@ -180,7 +180,8 @@ static dns_rdata_rrsig_t rrsig_test_data2 = {
 static bool
 ownercase_test_one(const char *str1, const char *str2) {
 	isc_result_t result;
-	uint8_t qpdb_s[sizeof(qpzonedb_t) + sizeof(qpzone_bucket_t)];
+	alignas(qpzonedb_t)
+		uint8_t qpdb_s[sizeof(qpzonedb_t) + sizeof(qpzone_bucket_t)];
 	qpzonedb_t *qpdb = (qpzonedb_t *)&qpdb_s;
 	*qpdb = (qpzonedb_t){
 		.common.methods = &qpdb_zonemethods,
@@ -345,7 +346,8 @@ verify_aaaa_records(dns_db_t *db, dns_dbversion_t *version,
 
 ISC_RUN_TEST_IMPL(setownercase) {
 	isc_result_t result;
-	uint8_t qpdb_s[sizeof(qpzonedb_t) + sizeof(qpzone_bucket_t)];
+	alignas(qpzonedb_t)
+		uint8_t qpdb_s[sizeof(qpzonedb_t) + sizeof(qpzone_bucket_t)];
 	qpzonedb_t *qpdb = (qpzonedb_t *)&qpdb_s;
 	*qpdb = (qpzonedb_t){
 		.common.methods = &qpdb_zonemethods,