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Simplified away wake_thread

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cached_thread_count can handle it alone.

Added "fast path": when thread is being added to the cache and there's
queued connection request, serve it immediately.

Part of MDEV-19515 - Improve connect speed
This commit is contained in:
Sergey Vojtovich
2019-05-18 20:43:29 +04:00
parent 34dfcbe3a6
commit 0bee021b78
1 changed files with 17 additions and 20 deletions
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37
sql/mysqld.cc
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@@ -350,7 +350,6 @@ static my_bool opt_short_log_format= 0, opt_silent_startup= 0;
bool my_disable_leak_check= false;
uint kill_cached_threads;
static uint wake_thread;
ulong max_used_connections;
volatile ulong cached_thread_count= 0;
static char *mysqld_user, *mysqld_chroot;
@@ -2666,6 +2665,8 @@ void unlink_thd(THD *thd)
CONNECT *cache_thread(THD *thd)
{
struct timespec abstime;
CONNECT *connect;
bool flushed= false;
DBUG_ENTER("cache_thread");
DBUG_ASSERT(thd);
set_timespec(abstime, THREAD_CACHE_TIMEOUT);
@@ -2682,40 +2683,36 @@ CONNECT *cache_thread(THD *thd)
#endif
mysql_mutex_lock(&LOCK_thread_cache);
if (cached_thread_count < thread_cache_size && !kill_cached_threads)
if ((connect= thread_cache.get()))
cached_thread_count++;
else if (cached_thread_count < thread_cache_size && !kill_cached_threads)
{
/* Don't kill the thread, just put it in cache for reuse */
DBUG_PRINT("info", ("Adding thread to cache"));
cached_thread_count++;
while (!wake_thread)
for (;;)
{
int error= mysql_cond_timedwait(&COND_thread_cache, &LOCK_thread_cache,
&abstime);
if (kill_cached_threads)
{
mysql_cond_signal(&COND_flush_thread_cache);
flushed= kill_cached_threads;
if ((connect= thread_cache.get()))
break;
}
if (error == ETIMEDOUT || error == ETIME)
else if (flushed || error == ETIMEDOUT || error == ETIME)
{
/*
If timeout, end thread.
If a new thread is requested (wake_thread is set), we will handle
If a new thread is requested, we will handle
the call, even if we got a timeout (as we are already awake and free)
*/
cached_thread_count--;
break;
}
}
cached_thread_count--;
if (auto connect= thread_cache.get())
{
wake_thread--;
mysql_mutex_unlock(&LOCK_thread_cache);
DBUG_RETURN(connect);
}
}
mysql_mutex_unlock(&LOCK_thread_cache);
DBUG_RETURN(0);
if (flushed)
mysql_cond_signal(&COND_flush_thread_cache);
DBUG_RETURN(connect);
}
@@ -6116,11 +6113,11 @@ void create_thread_to_handle_connection(CONNECT *connect)
DBUG_ENTER("create_thread_to_handle_connection");
mysql_mutex_lock(&LOCK_thread_cache);
if (cached_thread_count > wake_thread)
if (cached_thread_count)
{
/* Get thread from cache */
thread_cache.push_back(connect);
wake_thread++;
cached_thread_count--;
mysql_mutex_unlock(&LOCK_thread_cache);
mysql_cond_signal(&COND_thread_cache);
DBUG_PRINT("info",("Thread created"));
@@ -7896,7 +7893,7 @@ static int mysql_init_variables(void)
mqh_used= 0;
cleanup_done= 0;
test_flags= select_errors= dropping_tables= ha_open_options=0;
thread_count= kill_cached_threads= wake_thread= 0;
thread_count= kill_cached_threads= 0;
slave_open_temp_tables= 0;
cached_thread_count= 0;
opt_endinfo= using_udf_functions= 0;