1/* Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License as published by
5 the Free Software Foundation; version 2 of the License.
6
7 This program is distributed in the hope that it will be useful,
8 but WITHOUT ANY WARRANTY; without even the implied warranty of
9 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 GNU General Public License for more details.
11
12 You should have received a copy of the GNU General Public License
13 along with this program; if not, write to the Free Software
14 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
15
16#ifndef MYSQL_SERVICE_THD_WAIT_INCLUDED
17#define MYSQL_SERVICE_THD_WAIT_INCLUDED
18
19/**
20 @file include/mysql/service_thd_wait.h
21 This service provides functions for plugins and storage engines to report
22 when they are going to sleep/stall.
23
24 SYNOPSIS
25 thd_wait_begin() - call just before a wait begins
26 thd Thread object
27 Use NULL if the thd is NOT known.
28 wait_type Type of wait
29 1 -- short wait (e.g. for mutex)
30 2 -- medium wait (e.g. for disk io)
31 3 -- large wait (e.g. for locked row/table)
32 NOTES
33 This is used by the threadpool to have better knowledge of which
34 threads that currently are actively running on CPUs. When a thread
35 reports that it's going to sleep/stall, the threadpool scheduler is
36 free to start another thread in the pool most likely. The expected wait
37 time is simply an indication of how long the wait is expected to
38 become, the real wait time could be very different.
39
40 thd_wait_end() called immediately after the wait is complete
41
42 thd_wait_end() MUST be called if thd_wait_begin() was called.
43
44 Using thd_wait_...() service is optional but recommended. Using it will
45 improve performance as the thread pool will be more active at managing the
46 thread workload.
47*/
48
49#ifdef __cplusplus
50extern "C" {
51#endif
52
53/*
54 One should only report wait events that could potentially block for a
55 long time. A mutex wait is too short of an event to report. The reason
56 is that an event which is reported leads to a new thread starts
57 executing a query and this has a negative impact of usage of CPU caches
58 and thus the expected gain of starting a new thread must be higher than
59 the expected cost of lost performance due to starting a new thread.
60
61 Good examples of events that should be reported are waiting for row locks
62 that could easily be for many milliseconds or even seconds and the same
63 holds true for global read locks, table locks and other meta data locks.
64 Another event of interest is going to sleep for an extended time.
65*/
66typedef enum _thd_wait_type_e {
67 THD_WAIT_SLEEP= 1,
68 THD_WAIT_DISKIO= 2,
69 THD_WAIT_ROW_LOCK= 3,
70 THD_WAIT_GLOBAL_LOCK= 4,
71 THD_WAIT_META_DATA_LOCK= 5,
72 THD_WAIT_TABLE_LOCK= 6,
73 THD_WAIT_USER_LOCK= 7,
74 THD_WAIT_BINLOG= 8,
75 THD_WAIT_GROUP_COMMIT= 9,
76 THD_WAIT_SYNC= 10,
77 THD_WAIT_NET= 11,
78 THD_WAIT_LAST= 12
79} thd_wait_type;
80
81extern struct thd_wait_service_st {
82 void (*thd_wait_begin_func)(MYSQL_THD, int);
83 void (*thd_wait_end_func)(MYSQL_THD);
84} *thd_wait_service;
85
86#ifdef MYSQL_DYNAMIC_PLUGIN
87
88#define thd_wait_begin(_THD, _WAIT_TYPE) \
89 thd_wait_service->thd_wait_begin_func(_THD, _WAIT_TYPE)
90#define thd_wait_end(_THD) thd_wait_service->thd_wait_end_func(_THD)
91
92#else
93
94void thd_wait_begin(MYSQL_THD thd, int wait_type);
95void thd_wait_end(MYSQL_THD thd);
96
97#endif
98
99#ifdef __cplusplus
100}
101#endif
102
103#endif
104
105