PS-7626 - Use an ad-hoc mutex to read net_buffer_shrink_interval

ldonoso · Apr 7, 2021 · ecb6dfb · ecb6dfb
1 parent c3f4e1c
commit ecb6dfb
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Showing 4 changed files with 12 additions and 3 deletions.
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
@@ -1026,6 +1026,7 @@ static PSI_mutex_key key_LOCK_log_throttle_qni;
 static PSI_mutex_key key_LOCK_reset_gtid_table;
 static PSI_mutex_key key_LOCK_compress_gtid_table;
 static PSI_mutex_key key_LOCK_collect_instance_log;
+static PSI_mutex_key key_LOCK_net_buffer_shrink_interval;
 static PSI_mutex_key key_BINLOG_LOCK_commit;
 static PSI_mutex_key key_BINLOG_LOCK_commit_queue;
 static PSI_mutex_key key_BINLOG_LOCK_done;
@@ -1215,6 +1216,7 @@ mysql_mutex_t LOCK_password_history;
 mysql_mutex_t LOCK_password_reuse_interval;
 mysql_mutex_t LOCK_tls_ctx_options;
 mysql_mutex_t LOCK_admin_tls_ctx_options;
+mysql_mutex_t LOCK_net_buffer_shrink_interval;
 
 #if defined(ENABLED_DEBUG_SYNC)
 MYSQL_PLUGIN_IMPORT uint opt_debug_sync_timeout = 0;
@@ -2593,6 +2595,7 @@ static void clean_up_mutexes() {
   mysql_mutex_destroy(&LOCK_collect_instance_log);
   mysql_mutex_destroy(&LOCK_password_history);
   mysql_mutex_destroy(&LOCK_password_reuse_interval);
+  mysql_mutex_destroy(&LOCK_net_buffer_shrink_interval);
   mysql_cond_destroy(&COND_manager);
 #ifdef _WIN32
   mysql_cond_destroy(&COND_handler_count);
@@ -5229,6 +5232,8 @@ static int init_thread_environment() {
                    MY_MUTEX_INIT_FAST);
   mysql_mutex_init(key_LOCK_collect_instance_log, &LOCK_collect_instance_log,
                    MY_MUTEX_INIT_FAST);
+  mysql_mutex_init(key_LOCK_net_buffer_shrink_interval, &LOCK_net_buffer_shrink_interval,
+                   MY_MUTEX_INIT_FAST);
   mysql_cond_init(key_COND_compress_gtid_table, &COND_compress_gtid_table);
 
   mysql_mutex_init(key_LOCK_global_user_client_stats,
@@ -11502,6 +11507,7 @@ static PSI_mutex_info all_server_mutexes[]=
   { &key_LOCK_reset_gtid_table, "LOCK_reset_gtid_table", PSI_FLAG_SINGLETON, 0, PSI_DOCUMENT_ME},
   { &key_LOCK_compress_gtid_table, "LOCK_compress_gtid_table", PSI_FLAG_SINGLETON, 0, PSI_DOCUMENT_ME},
   { &key_LOCK_collect_instance_log, "LOCK_collect_instance_log", PSI_FLAG_SINGLETON, 0, PSI_DOCUMENT_ME},
+  { &key_LOCK_net_buffer_shrink_interval, "LOCK_net_buffer_shrink_interval", PSI_FLAG_SINGLETON, 0, PSI_DOCUMENT_ME},
   { &key_mts_gaq_LOCK, "key_mts_gaq_LOCK", 0, 0, PSI_DOCUMENT_ME},
   { &key_thd_timer_mutex, "thd_timer_mutex", 0, 0, PSI_DOCUMENT_ME},
   { &key_commit_order_manager_mutex, "Commit_order_manager::m_mutex", 0, 0, PSI_DOCUMENT_ME},

diff --git a/sql/mysqld.h b/sql/mysqld.h
@@ -725,6 +725,7 @@ extern mysql_mutex_t LOCK_collect_instance_log;
 extern mysql_mutex_t LOCK_tls_ctx_options;
 extern mysql_mutex_t LOCK_admin_tls_ctx_options;
 extern mysql_mutex_t LOCK_rotate_binlog_master_key;
+extern mysql_mutex_t LOCK_net_buffer_shrink_interval;
 
 extern mysql_cond_t COND_server_started;
 extern mysql_cond_t COND_compress_gtid_table;

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
@@ -1206,9 +1206,9 @@ void bind_fields(Item *first) {
  */
 static bool net_buffer_shrink_interval_is_over(
     const THD *const thd, unsigned long long net_buffer_shrink_time) {
-  mysql_mutex_lock(&LOCK_global_system_variables);
+  mysql_mutex_lock(&LOCK_net_buffer_shrink_interval);
   auto interval = net_buffer_shrink_interval;
-  mysql_mutex_unlock(&LOCK_global_system_variables);
+  mysql_mutex_unlock(&LOCK_net_buffer_shrink_interval);
 
   return interval != 0 &&
          thd->start_utime / 1000000 > net_buffer_shrink_time + interval;

diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
@@ -2800,14 +2800,16 @@ static Sys_var_ulong Sys_max_allowed_packet(
     BLOCK_SIZE(1024), NO_MUTEX_GUARD, NOT_IN_BINLOG,
     ON_CHECK(check_max_allowed_packet));
 
+static PolyLock_mutex PLock_sys_net_buffer_shrink_interval(&LOCK_net_buffer_shrink_interval);
+
 static Sys_var_ulong Sys_net_buffer_shrink_interval(
     "net_buffer_shrink_interval",
     "Check and maybe shrink network buffer with given frequency(seconds). "
     "It shrinks network buffer to the maximum packet size seen in previous "
     "net_buffer_shrink_interval seconds. "
     "Set to 0 to disable checks and shrinks",
     GLOBAL_VAR(net_buffer_shrink_interval), CMD_LINE(REQUIRED_ARG),
-    VALID_RANGE(0, LONG_TIMEOUT), DEFAULT(0), BLOCK_SIZE(1), NO_MUTEX_GUARD,
+    VALID_RANGE(0, LONG_TIMEOUT), DEFAULT(0), BLOCK_SIZE(1), &PLock_sys_net_buffer_shrink_interval,
     NOT_IN_BINLOG);
 
 static Sys_var_ulong Sys_slave_max_allowed_packet(