wait_event.h

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/*-------------------------------------------------------------------------
 * wait_event.h
 *    Definitions related to wait event reporting
 *
 * Copyright (c) 2001-2023, PostgreSQL Global Development Group
 *
 * src/include/utils/wait_event.h
 * ----------
 */
#ifndef WAIT_EVENT_H
#define WAIT_EVENT_H
 
 
/* ----------
 * Wait Classes
 * ----------
 */
#define PG_WAIT_LWLOCK              0x01000000U
#define PG_WAIT_LOCK                0x03000000U
#define PG_WAIT_BUFFERPIN           0x04000000U
#define PG_WAIT_ACTIVITY            0x05000000U
#define PG_WAIT_CLIENT              0x06000000U
#define PG_WAIT_EXTENSION           0x07000000U
#define PG_WAIT_IPC                 0x08000000U
#define PG_WAIT_TIMEOUT             0x09000000U
#define PG_WAIT_IO                  0x0A000000U
 
/* enums for wait events */
#include "utils/wait_event_types.h"
 
extern const char *pgstat_get_wait_event(uint32 wait_event_info);
extern const char *pgstat_get_wait_event_type(uint32 wait_event_info);
static inline void pgstat_report_wait_start(uint32 wait_event_info);
static inline void pgstat_report_wait_end(void);
extern void pgstat_set_wait_event_storage(uint32 *wait_event_info);
extern void pgstat_reset_wait_event_storage(void);
 
extern PGDLLIMPORT uint32 *my_wait_event_info;
 
 
/* ----------
 * Wait Events - Extension
 *
 * Use this category when the server process is waiting for some condition
 * defined by an extension module.
 *
 * Extensions can define their own wait events in this category.  They should
 * call WaitEventExtensionNew() with a wait event string.  If the wait event
 * associated to a string is already allocated, it returns the wait event
 * information to use.  If not, it gets one wait event ID allocated from
 * a shared counter, associates the string to the ID in the shared dynamic
 * hash and returns the wait event information.
 *
 * The ID retrieved can be used with pgstat_report_wait_start() or equivalent.
 */
typedef enum
{
    WAIT_EVENT_EXTENSION = PG_WAIT_EXTENSION,
    WAIT_EVENT_EXTENSION_FIRST_USER_DEFINED
} WaitEventExtension;
 
extern void WaitEventExtensionShmemInit(void);
extern Size WaitEventExtensionShmemSize(void);
 
extern uint32 WaitEventExtensionNew(const char *wait_event_name);
extern char **GetWaitEventExtensionNames(int *nwaitevents);
 
/* ----------
 * pgstat_report_wait_start() -
 *
 *  Called from places where server process needs to wait.  This is called
 *  to report wait event information.  The wait information is stored
 *  as 4-bytes where first byte represents the wait event class (type of
 *  wait, for different types of wait, refer WaitClass) and the next
 *  3-bytes represent the actual wait event.  Currently 2-bytes are used
 *  for wait event which is sufficient for current usage, 1-byte is
 *  reserved for future usage.
 *
 *  Historically we used to make this reporting conditional on
 *  pgstat_track_activities, but the check for that seems to add more cost
 *  than it saves.
 *
 *  my_wait_event_info initially points to local memory, making it safe to
 *  call this before MyProc has been initialized.
 * ----------
 */
static inline void
pgstat_report_wait_start(uint32 wait_event_info)
{
    /*
     * Since this is a four-byte field which is always read and written as
     * four-bytes, updates are atomic.
     */
    *(volatile uint32 *) my_wait_event_info = wait_event_info;
}
 
/* ----------
 * pgstat_report_wait_end() -
 *
 *  Called to report end of a wait.
 * ----------
 */
static inline void
pgstat_report_wait_end(void)
{
    /* see pgstat_report_wait_start() */
    *(volatile uint32 *) my_wait_event_info = 0;
}
 
 
#endif                          /* WAIT_EVENT_H */