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, version 2.0, 5 as published by the Free Software Foundation. 6 7 This program is also distributed with certain software (including 8 but not limited to OpenSSL) that is licensed under separate terms, 9 as designated in a particular file or component or in included license 10 documentation. The authors of MySQL hereby grant you an additional 11 permission to link the program and your derivative works with the 12 separately licensed software that they have included with MySQL. 13 14 This program is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License, version 2.0, for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with this program; if not, write to the Free Software 21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ 22 23 #ifndef MYSQL_SERVICE_THD_WAIT_INCLUDED 24 #define MYSQL_SERVICE_THD_WAIT_INCLUDED 25 26 /** 27 @file include/mysql/service_thd_wait.h 28 This service provides functions for plugins and storage engines to report 29 when they are going to sleep/stall. 30 31 SYNOPSIS 32 thd_wait_begin() - call just before a wait begins 33 thd Thread object 34 Use NULL if the thd is NOT known. 35 wait_type Type of wait 36 1 -- short wait (e.g. for mutex) 37 2 -- medium wait (e.g. for disk io) 38 3 -- large wait (e.g. for locked row/table) 39 NOTES 40 This is used by the threadpool to have better knowledge of which 41 threads that currently are actively running on CPUs. When a thread 42 reports that it's going to sleep/stall, the threadpool scheduler is 43 free to start another thread in the pool most likely. The expected wait 44 time is simply an indication of how long the wait is expected to 45 become, the real wait time could be very different. 46 47 thd_wait_end() called immediately after the wait is complete 48 49 thd_wait_end() MUST be called if thd_wait_begin() was called. 50 51 Using thd_wait_...() service is optional but recommended. Using it will 52 improve performance as the thread pool will be more active at managing the 53 thread workload. 54 */ 55 56 #ifdef __cplusplus 57 extern "C" { 58 #endif 59 60 /* 61 One should only report wait events that could potentially block for a 62 long time. A mutex wait is too short of an event to report. The reason 63 is that an event which is reported leads to a new thread starts 64 executing a query and this has a negative impact of usage of CPU caches 65 and thus the expected gain of starting a new thread must be higher than 66 the expected cost of lost performance due to starting a new thread. 67 68 Good examples of events that should be reported are waiting for row locks 69 that could easily be for many milliseconds or even seconds and the same 70 holds true for global read locks, table locks and other meta data locks. 71 Another event of interest is going to sleep for an extended time. 72 */ 73 typedef enum _thd_wait_type_e { 74 THD_WAIT_SLEEP= 1, 75 THD_WAIT_DISKIO= 2, 76 THD_WAIT_ROW_LOCK= 3, 77 THD_WAIT_GLOBAL_LOCK= 4, 78 THD_WAIT_META_DATA_LOCK= 5, 79 THD_WAIT_TABLE_LOCK= 6, 80 THD_WAIT_USER_LOCK= 7, 81 THD_WAIT_BINLOG= 8, 82 THD_WAIT_GROUP_COMMIT= 9, 83 THD_WAIT_SYNC= 10, 84 THD_WAIT_NET= 11, 85 THD_WAIT_LAST= 12 86 } thd_wait_type; 87 88 extern struct thd_wait_service_st { 89 void (*thd_wait_begin_func)(MYSQL_THD, int); 90 void (*thd_wait_end_func)(MYSQL_THD); 91 } *thd_wait_service; 92 93 #ifdef MYSQL_DYNAMIC_PLUGIN 94 95 #define thd_wait_begin(_THD, _WAIT_TYPE) \ 96 thd_wait_service->thd_wait_begin_func(_THD, _WAIT_TYPE) 97 #define thd_wait_end(_THD) thd_wait_service->thd_wait_end_func(_THD) 98 99 #else 100 101 void thd_wait_begin(MYSQL_THD thd, int wait_type); 102 void thd_wait_end(MYSQL_THD thd); 103 104 #endif 105 106 #ifdef __cplusplus 107 } 108 #endif 109 110 #endif 111 112