From 05faff6d5306de1e57b56f9ea44469bfb111e2e3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Wed, 15 Jan 2025 10:36:33 +0100
Subject: [PATCH] Remove memory limit on ADB finds and fetches

Address Database (ADB) shares the memory for the short lived ADB
objects (finds, fetches, addrinfo) and the long lived ADB
objects (names, entries, namehooks).  This could lead to a situation
where the resolver-heavy load would force evict ADB objects from the
database to point where ADB is completely empty, leading to even more
resolver-heavy load.

Make the short lived ADB objects use the other memory context that we
already created for the hashmaps.  This makes the ADB overmem condition
to not be triggered by the ongoing resolver fetches.
---
 lib/dns/adb.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/lib/dns/adb.c b/lib/dns/adb.c
index 23017a759a..56b2edf52c 100644
--- a/lib/dns/adb.c
+++ b/lib/dns/adb.c
@@ -1112,7 +1112,7 @@ static dns_adbfind_t *
 new_adbfind(dns_adb_t *adb, in_port_t port) {
 	dns_adbfind_t *find = NULL;
 
-	find = isc_mem_get(adb->mctx, sizeof(*find));
+	find = isc_mem_get(adb->hmctx, sizeof(*find));
 	*find = (dns_adbfind_t){
 		.port = port,
 		.result_v4 = ISC_R_UNEXPECTED,
@@ -1151,7 +1151,7 @@ free_adbfind(dns_adbfind_t **findp) {
 
 	isc_mutex_destroy(&find->lock);
 
-	isc_mem_put(adb->mctx, find, sizeof(*find));
+	isc_mem_put(adb->hmctx, find, sizeof(*find));
 	dns_adb_detach(&adb);
 }
 
@@ -1159,7 +1159,7 @@ static dns_adbfetch_t *
 new_adbfetch(dns_adb_t *adb) {
 	dns_adbfetch_t *fetch = NULL;
 
-	fetch = isc_mem_get(adb->mctx, sizeof(*fetch));
+	fetch = isc_mem_get(adb->hmctx, sizeof(*fetch));
 	*fetch = (dns_adbfetch_t){ 0 };
 	dns_rdataset_init(&fetch->rdataset);
 
@@ -1183,7 +1183,7 @@ free_adbfetch(dns_adb_t *adb, dns_adbfetch_t **fetchp) {
 		dns_rdataset_disassociate(&fetch->rdataset);
 	}
 
-	isc_mem_put(adb->mctx, fetch, sizeof(*fetch));
+	isc_mem_put(adb->hmctx, fetch, sizeof(*fetch));
 }
 
 /*
@@ -1194,7 +1194,7 @@ static dns_adbaddrinfo_t *
 new_adbaddrinfo(dns_adb_t *adb, dns_adbentry_t *entry, in_port_t port) {
 	dns_adbaddrinfo_t *ai = NULL;
 
-	ai = isc_mem_get(adb->mctx, sizeof(*ai));
+	ai = isc_mem_get(adb->hmctx, sizeof(*ai));
 	*ai = (dns_adbaddrinfo_t){
 		.srtt = atomic_load(&entry->srtt),
 		.flags = atomic_load(&entry->flags),
@@ -1227,7 +1227,7 @@ free_adbaddrinfo(dns_adb_t *adb, dns_adbaddrinfo_t **ainfo) {
 	}
 	dns_adbentry_detach(&ai->entry);
 
-	isc_mem_put(adb->mctx, ai, sizeof(*ai));
+	isc_mem_put(adb->hmctx, ai, sizeof(*ai));
 }
 
 static bool
@@ -1863,7 +1863,7 @@ dns_adb_create(isc_mem_t *mem, dns_view_t *view, dns_adb_t **newadb) {
 	isc_mem_attach(mem, &adb->mctx);
 
 	isc_mem_create(&adb->hmctx);
-	isc_mem_setname(adb->hmctx, "ADB_hashmaps");
+	isc_mem_setname(adb->hmctx, "ADB_dynamic");
 
 	isc_hashmap_create(adb->hmctx, ADB_HASH_BITS, &adb->names);
 	isc_rwlock_init(&adb->names_lock);