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Added copiright, some more comments

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This commit is contained in:
Vladislav Vaintroub
2012-02-17 23:27:15 +01:00
parent b932e57b27
commit 2a5d8ea9a2
3 changed files with 81 additions and 6 deletions
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14
sql/threadpool.h
View File

@ -1,3 +1,17 @@
/* Copyright (C) 2012 Monty Program Ab
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#define MAX_THREAD_GROUPS 128

27
sql/threadpool_common.cc
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@ -1,3 +1,18 @@
/* Copyright (C) 2012 Monty Program Ab
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#include <my_global.h>
#include <violite.h>
#include <sql_priv.h>
@ -171,6 +186,9 @@ void threadpool_remove_connection(THD *thd)
worker_context.restore();
}
/**
Process a single client request or a single batch.
*/
int threadpool_process_request(THD *thd)
{
int retval= 0;
@ -190,6 +208,15 @@ int threadpool_process_request(THD *thd)
}
/*
In the loop below, the flow is essentially the copy of thead-per-connections
logic, see do_handle_one_connection() in sql_connect.c
The goal is to execute a single query, thus the loop is normally executed
only once. However for SSL connections, it can be executed multiple times
(SSL can preread and cache incoming data, and vio->has_data() checks if it
was the case).
*/
for(;;)
{
Vio *vio;

46
sql/threadpool_unix.cc
View File

@ -1,3 +1,18 @@
/* Copyright (C) 2012 Monty Program Ab
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#include <my_global.h>
#include <violite.h>
#include <sql_priv.h>
@ -541,6 +556,29 @@ void check_stall(thread_group_t *thread_group)
/*
Check whether requests from the workqueue are being dequeued.
The stall detection and resolution works as follows:
1. There is a counter thread_group->queue_event_count for the number of
events removed from the queue. Timer resets the counter to 0 on each run.
2. Timer determines stall if this counter remains 0 since last check
and the queue is not empty.
3. Once timer determined a stall it sets thread_group->stalled flag and
wakes and idle worker (or creates a new one, subject to throttling).
4. The stalled flag is reset, when an event is dequeued.
Q : Will this handling lead to an unbound growth of threads, if queue
stalls permanently?
A : No. If queue stalls permanently, it is an indication for many very long
simultaneous queries. The maximum number of simultanoues queries is
max_connections, further we have threadpool_max_threads limit, upon which no
worker threads are created. So in case there is a flood of very long
queries, threadpool would slowly approach thread-per-connection behavior.
NOTE:
If long queries never wait, creation of the new threads is done by timer,
so it is slower than in real thread-per-connection. However if long queries
do wait and indicate that via thd_wait_begin/end callbacks, thread creation
will be faster.
*/
if (!thread_group->queue.is_empty() && !thread_group->queue_event_count)
{
@ -1250,10 +1288,7 @@ void tp_post_kill_notification(THD *thd)
void tp_wait_begin(THD *thd, int type)
{
DBUG_ENTER("tp_wait_begin");
if (!thd)
DBUG_VOID_RETURN;
DBUG_ASSERT(thd);
connection_t *connection = (connection_t *)thd->event_scheduler.data;
if (connection)
{
@ -1272,8 +1307,7 @@ void tp_wait_begin(THD *thd, int type)
void tp_wait_end(THD *thd)
{
DBUG_ENTER("tp_wait_end");
if (!thd)
DBUG_VOID_RETURN;
DBUG_ASSERT(thd);
connection_t *connection = (connection_t *)thd->event_scheduler.data;
if (connection)