src/include/utils/wait_event.h

   1 /*-------------------------------------------------------------------------
   2  * wait_event.h
   3  *        Definitions related to wait event reporting
   4  *
   5  * Copyright (c) 2001-2023, PostgreSQL Global Development Group
   6  *
   7  * src/include/utils/wait_event.h
   8  * ----------
   9  */
  10 #ifndef WAIT_EVENT_H
  11 #define WAIT_EVENT_H
  12
  13
  14 /* ----------
  15  * Wait Classes
  16  * ----------
  17  */
  18 #define PG_WAIT_LWLOCK                          0x01000000U
  19 #define PG_WAIT_LOCK                            0x03000000U
  20 #define PG_WAIT_BUFFERPIN                       0x04000000U
  21 #define PG_WAIT_ACTIVITY                        0x05000000U
  22 #define PG_WAIT_CLIENT                          0x06000000U
  23 #define PG_WAIT_EXTENSION                       0x07000000U
  24 #define PG_WAIT_IPC                                     0x08000000U
  25 #define PG_WAIT_TIMEOUT                         0x09000000U
  26 #define PG_WAIT_IO                                      0x0A000000U
  27
  28 /* enums for wait events */
  29 #include "utils/wait_event_types.h"
  30
  31 extern const char *pgstat_get_wait_event(uint32 wait_event_info);
  32 extern const char *pgstat_get_wait_event_type(uint32 wait_event_info);
  33 static inline void pgstat_report_wait_start(uint32 wait_event_info);
  34 static inline void pgstat_report_wait_end(void);
  35 extern void pgstat_set_wait_event_storage(uint32 *wait_event_info);
  36 extern void pgstat_reset_wait_event_storage(void);
  37
  38 extern PGDLLIMPORT uint32 *my_wait_event_info;
  39
  40
  41 /* ----------
  42  * Wait Events - Extension
  43  *
  44  * Use this category when the server process is waiting for some condition
  45  * defined by an extension module.
  46  *
  47  * Extensions can define their own wait events in this category.  They should
  48  * call WaitEventExtensionNew() with a wait event string.  If the wait event
  49  * associated to a string is already allocated, it returns the wait event
  50  * information to use.  If not, it gets one wait event ID allocated from
  51  * a shared counter, associates the string to the ID in the shared dynamic
  52  * hash and returns the wait event information.
  53  *
  54  * The ID retrieved can be used with pgstat_report_wait_start() or equivalent.
  55  */
  56 typedef enum
  57 {
  58         WAIT_EVENT_EXTENSION = PG_WAIT_EXTENSION,
  59         WAIT_EVENT_EXTENSION_FIRST_USER_DEFINED
  60 } WaitEventExtension;
  61
  62 extern void WaitEventExtensionShmemInit(void);
  63 extern Size WaitEventExtensionShmemSize(void);
  64
  65 extern uint32 WaitEventExtensionNew(const char *wait_event_name);
  66
  67 /* ----------
  68  * pgstat_report_wait_start() -
  69  *
  70  *      Called from places where server process needs to wait.  This is called
  71  *      to report wait event information.  The wait information is stored
  72  *      as 4-bytes where first byte represents the wait event class (type of
  73  *      wait, for different types of wait, refer WaitClass) and the next
  74  *      3-bytes represent the actual wait event.  Currently 2-bytes are used
  75  *      for wait event which is sufficient for current usage, 1-byte is
  76  *      reserved for future usage.
  77  *
  78  *      Historically we used to make this reporting conditional on
  79  *      pgstat_track_activities, but the check for that seems to add more cost
  80  *      than it saves.
  81  *
  82  *      my_wait_event_info initially points to local memory, making it safe to
  83  *      call this before MyProc has been initialized.
  84  * ----------
  85  */
  86 static inline void
  87 pgstat_report_wait_start(uint32 wait_event_info)
  88 {
  89         /*
  90          * Since this is a four-byte field which is always read and written as
  91          * four-bytes, updates are atomic.
  92          */
  93         *(volatile uint32 *) my_wait_event_info = wait_event_info;
  94 }
  95
  96 /* ----------
  97  * pgstat_report_wait_end() -
  98  *
  99  *      Called to report end of a wait.
 100  * ----------
 101  */
 102 static inline void
 103 pgstat_report_wait_end(void)
 104 {
 105         /* see pgstat_report_wait_start() */
 106         *(volatile uint32 *) my_wait_event_info = 0;
 107 }
 108
 109
 110 #endif                                                  /* WAIT_EVENT_H */