Auto-configure '-slabs' values (#1276)

- Auto-configure '-slabs' values to a power of 2 value close to num-threads
  by default for multi-threaded environments.

Co-authored-by: Wouter Wijngaards <wcawijngaards@users.noreply.github.com>

doc/unbound.conf.5.in

@@ -259,9 +259,12 @@ A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
 or gigabytes (1024*1024 bytes in a megabyte).
 .TP
 .B msg\-cache\-slabs: \fI<number>
-Number of slabs in the message cache. Slabs reduce lock contention by threads.
-Must be set to a power of 2. Setting (close) to the number of cpus is a
-reasonable guess.
+Number of slabs in the message cache.
+Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .TP
 .B num\-queries\-per\-thread: \fI<number>
 The number of queries that every thread will service simultaneously.
@@ -400,8 +403,12 @@ A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
 or gigabytes (1024*1024 bytes in a megabyte).
 .TP
 .B rrset\-cache\-slabs: \fI<number>
-Number of slabs in the RRset cache. Slabs reduce lock contention by threads.
+Number of slabs in the RRset cache.
+Slabs reduce lock contention by threads.
 Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .TP
 .B cache\-max\-ttl: \fI<seconds>
 Time to live maximum for RRsets and messages in the cache. Default is
@@ -436,8 +443,12 @@ Time to live for entries in the host cache. The host cache contains
 roundtrip timing, lameness and EDNS support information. Default is 900.
 .TP
 .B infra\-cache\-slabs: \fI<number>
-Number of slabs in the infrastructure cache. Slabs reduce lock contention
-by threads. Must be set to a power of 2.
+Number of slabs in the infrastructure cache.
+Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .TP
 .B infra\-cache\-numhosts: \fI<number>
 Number of hosts for which information is cached. Default is 10000.
@@ -1494,9 +1505,12 @@ A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
 or gigabytes (1024*1024 bytes in a megabyte).
 .TP
 .B key\-cache\-slabs: \fI<number>
-Number of slabs in the key cache. Slabs reduce lock contention by threads.
-Must be set to a power of 2. Setting (close) to the number of cpus is a
-reasonable guess.
+Number of slabs in the key cache.
+Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .TP
 .B neg\-cache\-size: \fI<number>
 Number of bytes size of the aggressive negative cache. Default is 1 megabyte.
@@ -1903,9 +1917,12 @@ The ratelimit structure is small, so this data structure likely does
 not need to be large.
 .TP 5
 .B ratelimit\-slabs: \fI<number>
-Give power of 2 number of slabs, this is used to reduce lock contention
-in the ratelimit tracking data structure.  Close to the number of cpus is
-a fairly good setting.
+Number of slabs in the ratelimit tracking data structure.
+Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .TP 5
 .B ratelimit\-factor: \fI<number>
 Set the amount of queries to rate limit when the limit is exceeded.
@@ -1974,9 +1991,12 @@ The ip ratelimit structure is small, so this data structure likely does
 not need to be large.
 .TP 5
 .B ip\-ratelimit\-slabs: \fI<number>
-Give power of 2 number of slabs, this is used to reduce lock contention
-in the ip ratelimit tracking data structure.  Close to the number of cpus is
-a fairly good setting.
+Number of slabs in the ip ratelimit tracking data structure.
+Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .TP 5
 .B ip\-ratelimit\-factor: \fI<number>
 Set the amount of queries to rate limit when the limit is exceeded.
@@ -2610,9 +2630,12 @@ The shared secret cache is used when a same client is making multiple queries
 using the same public key. It saves a substantial amount of CPU.
 .TP
 .B dnscrypt\-shared\-secret\-cache\-slabs: \fI<number>
-Give power of 2 number of slabs, this is used to reduce lock contention
-in the dnscrypt shared secrets cache.  Close to the number of cpus is
-a fairly good setting.
+Number of slabs in the dnscrypt shared secrets cache.
+Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .TP
 .B dnscrypt\-nonce\-cache\-size: \fI<memory size>
 Give the size of the data structure in which the client nonces are kept in.
@@ -2621,9 +2644,12 @@ The nonce cache is used to prevent dnscrypt message replaying. Client nonce
 should be unique for any pair of client pk/server sk.
 .TP
 .B dnscrypt\-nonce\-cache\-slabs: \fI<number>
-Give power of 2 number of slabs, this is used to reduce lock contention
-in the dnscrypt nonce cache.  Close to the number of cpus is
-a fairly good setting.
+Number of slabs in the dnscrypt nonce cache.
+Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+Setting (close) to the number of cpus is a fairly good setting.
+If left unconfigured, it will be configured automatically to be a power of 2
+close to the number of configured threads in multi-threaded environments.
 .SS "EDNS Client Subnet Module Options"
 .LP
 The ECS module must be configured in the \fBmodule\-config:\fR directive e.g.,

testcode/unitauth.c

@@ -670,6 +670,7 @@ authtest_addzone(struct auth_zones* az, const char* name, char* fname)
 	auth_zone_set_zonefile(z, fname);
 	z->for_upstream = 1;
 	cfg = config_create();
+	config_auto_slab_values(cfg);
 	free(cfg->chrootdir);
 	cfg->chrootdir = NULL;
 

testcode/unitinfra.c

@@ -131,6 +131,7 @@ void infra_test(void)
 	unit_show_feature("infra cache");
 	unit_assert(ipstrtoaddr("127.0.0.1", 53, &one, &onelen));
 
+	config_auto_slab_values(cfg);
 	slab = infra_create(cfg);
 	/* insert new record */
 	unit_assert( infra_host(slab, &one, onelen, zone, zonelen, now,

testcode/unitzonemd.c

@@ -267,6 +267,7 @@ static void zonemd_verify_test(char* zname, char* zfile, char* tastr,
 	env.cfg = config_create();
 	if(!env.cfg)
 		fatal_exit("out of memory");
+	config_auto_slab_values(env.cfg);
 	env.now = &now;
 	env.cfg->val_date_override = cfg_convert_timeval(date_override);
 	if(!env.cfg->val_date_override)

util/config_file.c

@@ -169,10 +169,10 @@ config_create(void)
 	cfg->edns_buffer_size = 1232; /* from DNS flagday recommendation */
 	cfg->msg_buffer_size = 65552; /* 64 k + a small margin */
 	cfg->msg_cache_size = 4 * 1024 * 1024;
-	cfg->msg_cache_slabs = 4;
+	cfg->msg_cache_slabs = 0;
 	cfg->jostle_time = 200;
 	cfg->rrset_cache_size = 4 * 1024 * 1024;
-	cfg->rrset_cache_slabs = 4;
+	cfg->rrset_cache_slabs = 0;
 	cfg->host_ttl = 900;
 	cfg->bogus_ttl = 60;
 	cfg->min_ttl = 0;
@@ -182,7 +182,7 @@ config_create(void)
 	cfg->prefetch = 0;
 	cfg->prefetch_key = 0;
 	cfg->deny_any = 0;
-	cfg->infra_cache_slabs = 4;
+	cfg->infra_cache_slabs = 0;
 	cfg->infra_cache_numhosts = 10000;
 	cfg->infra_cache_min_rtt = 50;
 	cfg->infra_cache_max_rtt = 120000;
@@ -291,7 +291,7 @@ config_create(void)
 	cfg->keep_missing = 366*24*3600; /* one year plus a little leeway */
 	cfg->permit_small_holddown = 0;
 	cfg->key_cache_size = 4 * 1024 * 1024;
-	cfg->key_cache_slabs = 4;
+	cfg->key_cache_slabs = 0;
 	cfg->neg_cache_size = 1 * 1024 * 1024;
 	cfg->local_zones = NULL;
 	cfg->local_zones_nodefault = NULL;
@@ -341,8 +341,8 @@ config_create(void)
 	cfg->ip_ratelimit_cookie = 0;
 	cfg->ip_ratelimit = 0;
 	cfg->ratelimit = 0;
-	cfg->ip_ratelimit_slabs = 4;
-	cfg->ratelimit_slabs = 4;
+	cfg->ip_ratelimit_slabs = 0;
+	cfg->ratelimit_slabs = 0;
 	cfg->ip_ratelimit_size = 4*1024*1024;
 	cfg->ratelimit_size = 4*1024*1024;
 	cfg->ratelimit_for_domain = NULL;
@@ -367,9 +367,9 @@ config_create(void)
 	cfg->dnscrypt_provider_cert_rotated = NULL;
 	cfg->dnscrypt_secret_key = NULL;
 	cfg->dnscrypt_shared_secret_cache_size = 4*1024*1024;
-	cfg->dnscrypt_shared_secret_cache_slabs = 4;
+	cfg->dnscrypt_shared_secret_cache_slabs = 0;
 	cfg->dnscrypt_nonce_cache_size = 4*1024*1024;
-	cfg->dnscrypt_nonce_cache_slabs = 4;
+	cfg->dnscrypt_nonce_cache_slabs = 0;
 	cfg->pad_responses = 1;
 	cfg->pad_responses_block_size = 468; /* from RFC8467 */
 	cfg->pad_queries = 1;
@@ -454,6 +454,11 @@ struct config_file* config_create_forlib(void)
 	cfg->val_log_squelch = 1;
 	cfg->minimal_responses = 0;
 	cfg->harden_short_bufsize = 1;
+	/* Need to explicitly define the slabs from their 0 default value */
+	cfg->ip_ratelimit_slabs = 1;
+	cfg->ratelimit_slabs = 1;
+	cfg->dnscrypt_shared_secret_cache_slabs = 1;
+	cfg->dnscrypt_nonce_cache_slabs = 1;
 	return cfg;
 }
 
@@ -1448,6 +1453,41 @@ create_cfg_parser(struct config_file* cfg, char* filename, const char* chroot)
 	init_cfg_parse();
 }
 
+void
+config_auto_slab_values(struct config_file* cfg)
+{
+#define SET_AUTO_SLAB(var, name, val)						\
+do {										\
+	if(cfg->var == 0) {							\
+		cfg->var = val;							\
+		verbose(VERB_QUERY, "setting "name": %lu", (unsigned long)val);	\
+	}									\
+} while(0);
+#ifdef THREADS_DISABLED
+	size_t pow_2_threads = 1;
+#else
+	size_t pow_2_threads = 4;  /* pow2 start */
+	while (pow_2_threads < (size_t)(cfg->num_threads?cfg->num_threads:1) &&
+		/* 1/3 of the distance to the next pow2 value stays with the
+		 * lower value */
+		(size_t)cfg->num_threads > pow_2_threads + (pow_2_threads - 1)/3) {
+		pow_2_threads <<= 1;
+	}
+	log_assert((pow_2_threads & (pow_2_threads - 1)) == 0); /* powerof2? */
+#endif /* THREADS_DISABLED */
+
+	SET_AUTO_SLAB(msg_cache_slabs, "msg-cache-slabs", pow_2_threads);
+	SET_AUTO_SLAB(rrset_cache_slabs, "rrset-cache-slabs", pow_2_threads);
+	SET_AUTO_SLAB(infra_cache_slabs, "infra-cache-slabs", pow_2_threads);
+	SET_AUTO_SLAB(key_cache_slabs, "key-cache-slabs", pow_2_threads);
+	SET_AUTO_SLAB(ip_ratelimit_slabs, "ip-ratelimit-slabs", pow_2_threads);
+	SET_AUTO_SLAB(ratelimit_slabs, "ratelimit-slabs", pow_2_threads);
+	SET_AUTO_SLAB(dnscrypt_shared_secret_cache_slabs,
+		"dnscrypt-shared-secret-cache-slabs", pow_2_threads);
+	SET_AUTO_SLAB(dnscrypt_nonce_cache_slabs,
+		"dnscrypt-nonce-cache-slabs", pow_2_threads);
+}
+
 int
 config_read(struct config_file* cfg, const char* filename, const char* chroot)
 {
@@ -1512,6 +1552,7 @@ config_read(struct config_file* cfg, const char* filename, const char* chroot)
 			}
 		}
 		globfree(&g);
+		config_auto_slab_values(cfg);
 		return 1;
 	}
 #endif /* HAVE_GLOB */
@@ -1535,6 +1576,7 @@ config_read(struct config_file* cfg, const char* filename, const char* chroot)
 		return 0;
 	}
 
+	config_auto_slab_values(cfg);
 	return 1;
 }
 

util/config_file.h

@@ -966,6 +966,17 @@ struct config_file* config_create(void);
  */
 struct config_file* config_create_forlib(void);
 
+/**
+ * If _slabs values are not explicitly configured, 0 value, put them in a
+ * pow2 value close to the number of threads used.
+ * Starts at the current default 4.
+ * If num_threads is in between two pow2 values, 1/3 of the way stays with
+ * the lower pow2 value.
+ * Exported for unit testing.
+ * @param config: where the _slabs values reside.
+ */
+void config_auto_slab_values(struct config_file* config);
+
 /**
  * Read the config file from the specified filename.
  * @param config: where options are stored into, must be freshly created.