Line data    Source code

       1             : /* -------------------------------------------------------------------------
       2             :  *
       3             :  * pgstat_slru.c
       4             :  *    Implementation of SLRU statistics.
       5             :  *
       6             :  * This file contains the implementation of SLRU statistics. It is kept
       7             :  * separate from pgstat.c to enforce the line between the statistics access /
       8             :  * storage implementation and the details about individual types of
       9             :  * statistics.
      10             :  *
      11             :  * Copyright (c) 2001-2025, PostgreSQL Global Development Group
      12             :  *
      13             :  * IDENTIFICATION
      14             :  *    src/backend/utils/activity/pgstat_slru.c
      15             :  * -------------------------------------------------------------------------
      16             :  */
      17             : 
      18             : #include "postgres.h"
      19             : 
      20             : #include "utils/pgstat_internal.h"
      21             : #include "utils/timestamp.h"
      22             : 
      23             : 
      24             : static inline PgStat_SLRUStats *get_slru_entry(int slru_idx);
      25             : static void pgstat_reset_slru_counter_internal(int index, TimestampTz ts);
      26             : 
      27             : 
      28             : /*
      29             :  * SLRU statistics counts waiting to be flushed out.  We assume this variable
      30             :  * inits to zeroes.  Entries are one-to-one with slru_names[].  Changes of
      31             :  * SLRU counters are reported within critical sections so we use static memory
      32             :  * in order to avoid memory allocation.
      33             :  */
      34             : static PgStat_SLRUStats pending_SLRUStats[SLRU_NUM_ELEMENTS];
      35             : static bool have_slrustats = false;
      36             : 
      37             : 
      38             : /*
      39             :  * Reset counters for a single SLRU.
      40             :  *
      41             :  * Permission checking for this function is managed through the normal
      42             :  * GRANT system.
      43             :  */
      44             : void
      45           6 : pgstat_reset_slru(const char *name)
      46             : {
      47           6 :     TimestampTz ts = GetCurrentTimestamp();
      48             : 
      49             :     Assert(name != NULL);
      50             : 
      51           6 :     pgstat_reset_slru_counter_internal(pgstat_get_slru_index(name), ts);
      52           6 : }
      53             : 
      54             : /*
      55             :  * SLRU statistics count accumulation functions --- called from slru.c
      56             :  */
      57             : 
      58             : void
      59    14679118 : pgstat_count_slru_page_zeroed(int slru_idx)
      60             : {
      61    14679118 :     get_slru_entry(slru_idx)->blocks_zeroed += 1;
      62    14679118 : }
      63             : 
      64             : void
      65     1762434 : pgstat_count_slru_page_hit(int slru_idx)
      66             : {
      67     1762434 :     get_slru_entry(slru_idx)->blocks_hit += 1;
      68     1762434 : }
      69             : 
      70             : void
      71         200 : pgstat_count_slru_page_exists(int slru_idx)
      72             : {
      73         200 :     get_slru_entry(slru_idx)->blocks_exists += 1;
      74         200 : }
      75             : 
      76             : void
      77        3874 : pgstat_count_slru_page_read(int slru_idx)
      78             : {
      79        3874 :     get_slru_entry(slru_idx)->blocks_read += 1;
      80        3874 : }
      81             : 
      82             : void
      83    14681856 : pgstat_count_slru_page_written(int slru_idx)
      84             : {
      85    14681856 :     get_slru_entry(slru_idx)->blocks_written += 1;
      86    14681856 : }
      87             : 
      88             : void
      89       16640 : pgstat_count_slru_flush(int slru_idx)
      90             : {
      91       16640 :     get_slru_entry(slru_idx)->flush += 1;
      92       16640 : }
      93             : 
      94             : void
      95        3450 : pgstat_count_slru_truncate(int slru_idx)
      96             : {
      97        3450 :     get_slru_entry(slru_idx)->truncate += 1;
      98        3450 : }
      99             : 
     100             : /*
     101             :  * Support function for the SQL-callable pgstat* functions. Returns
     102             :  * a pointer to the slru statistics struct.
     103             :  */
     104             : PgStat_SLRUStats *
     105         124 : pgstat_fetch_slru(void)
     106             : {
     107         124 :     pgstat_snapshot_fixed(PGSTAT_KIND_SLRU);
     108             : 
     109         124 :     return pgStatLocal.snapshot.slru;
     110             : }
     111             : 
     112             : /*
     113             :  * Returns SLRU name for an index. The index may be above SLRU_NUM_ELEMENTS,
     114             :  * in which case this returns NULL. This allows writing code that does not
     115             :  * know the number of entries in advance.
     116             :  */
     117             : const char *
     118        1116 : pgstat_get_slru_name(int slru_idx)
     119             : {
     120        1116 :     if (slru_idx < 0 || slru_idx >= SLRU_NUM_ELEMENTS)
     121         124 :         return NULL;
     122             : 
     123         992 :     return slru_names[slru_idx];
     124             : }
     125             : 
     126             : /*
     127             :  * Determine index of entry for a SLRU with a given name. If there's no exact
     128             :  * match, returns index of the last "other" entry used for SLRUs defined in
     129             :  * external projects.
     130             :  */
     131             : int
     132       14710 : pgstat_get_slru_index(const char *name)
     133             : {
     134             :     int         i;
     135             : 
     136       58842 :     for (i = 0; i < SLRU_NUM_ELEMENTS; i++)
     137             :     {
     138       58838 :         if (strcmp(slru_names[i], name) == 0)
     139       14706 :             return i;
     140             :     }
     141             : 
     142             :     /* return index of the last entry (which is the "other" one) */
     143           4 :     return (SLRU_NUM_ELEMENTS - 1);
     144             : }
     145             : 
     146             : /*
     147             :  * Check if there are any SLRU stats entries waiting for flush.
     148             :  */
     149             : bool
     150       14826 : pgstat_slru_have_pending_cb(void)
     151             : {
     152       14826 :     return have_slrustats;
     153             : }
     154             : 
     155             : /*
     156             :  * Flush out locally pending SLRU stats entries
     157             :  *
     158             :  * If nowait is true, this function returns false on lock failure. Otherwise
     159             :  * this function always returns true.
     160             :  *
     161             :  * If nowait is true, this function returns true if the lock could not be
     162             :  * acquired. Otherwise return false.
     163             :  */
     164             : bool
     165       70376 : pgstat_slru_flush_cb(bool nowait)
     166             : {
     167       70376 :     PgStatShared_SLRU *stats_shmem = &pgStatLocal.shmem->slru;
     168             :     int         i;
     169             : 
     170       70376 :     if (!have_slrustats)
     171       46920 :         return false;
     172             : 
     173       23456 :     if (!nowait)
     174       19862 :         LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
     175        3594 :     else if (!LWLockConditionalAcquire(&stats_shmem->lock, LW_EXCLUSIVE))
     176           0 :         return true;
     177             : 
     178      211104 :     for (i = 0; i < SLRU_NUM_ELEMENTS; i++)
     179             :     {
     180      187648 :         PgStat_SLRUStats *sharedent = &stats_shmem->stats[i];
     181      187648 :         PgStat_SLRUStats *pendingent = &pending_SLRUStats[i];
     182             : 
     183             : #define SLRU_ACC(fld) sharedent->fld += pendingent->fld
     184      187648 :         SLRU_ACC(blocks_zeroed);
     185      187648 :         SLRU_ACC(blocks_hit);
     186      187648 :         SLRU_ACC(blocks_read);
     187      187648 :         SLRU_ACC(blocks_written);
     188      187648 :         SLRU_ACC(blocks_exists);
     189      187648 :         SLRU_ACC(flush);
     190      187648 :         SLRU_ACC(truncate);
     191             : #undef SLRU_ACC
     192             :     }
     193             : 
     194             :     /* done, clear the pending entry */
     195     1524640 :     MemSet(pending_SLRUStats, 0, sizeof(pending_SLRUStats));
     196             : 
     197       23456 :     LWLockRelease(&stats_shmem->lock);
     198             : 
     199       23456 :     have_slrustats = false;
     200             : 
     201       23456 :     return false;
     202             : }
     203             : 
     204             : void
     205        2100 : pgstat_slru_init_shmem_cb(void *stats)
     206             : {
     207        2100 :     PgStatShared_SLRU *stats_shmem = (PgStatShared_SLRU *) stats;
     208             : 
     209        2100 :     LWLockInitialize(&stats_shmem->lock, LWTRANCHE_PGSTATS_DATA);
     210        2100 : }
     211             : 
     212             : void
     213         462 : pgstat_slru_reset_all_cb(TimestampTz ts)
     214             : {
     215        4158 :     for (int i = 0; i < SLRU_NUM_ELEMENTS; i++)
     216        3696 :         pgstat_reset_slru_counter_internal(i, ts);
     217         462 : }
     218             : 
     219             : void
     220        1356 : pgstat_slru_snapshot_cb(void)
     221             : {
     222        1356 :     PgStatShared_SLRU *stats_shmem = &pgStatLocal.shmem->slru;
     223             : 
     224        1356 :     LWLockAcquire(&stats_shmem->lock, LW_SHARED);
     225             : 
     226        1356 :     memcpy(pgStatLocal.snapshot.slru, &stats_shmem->stats,
     227             :            sizeof(stats_shmem->stats));
     228             : 
     229        1356 :     LWLockRelease(&stats_shmem->lock);
     230        1356 : }
     231             : 
     232             : /*
     233             :  * Returns pointer to entry with counters for given SLRU (based on the name
     234             :  * stored in SlruCtl as lwlock tranche name).
     235             :  */
     236             : static inline PgStat_SLRUStats *
     237    31147572 : get_slru_entry(int slru_idx)
     238             : {
     239             :     pgstat_assert_is_up();
     240             : 
     241             :     /*
     242             :      * The postmaster should never register any SLRU statistics counts; if it
     243             :      * did, the counts would be duplicated into child processes via fork().
     244             :      */
     245             :     Assert(IsUnderPostmaster || !IsPostmasterEnvironment);
     246             : 
     247             :     Assert((slru_idx >= 0) && (slru_idx < SLRU_NUM_ELEMENTS));
     248             : 
     249    31147572 :     have_slrustats = true;
     250             : 
     251    31147572 :     return &pending_SLRUStats[slru_idx];
     252             : }
     253             : 
     254             : static void
     255        3702 : pgstat_reset_slru_counter_internal(int index, TimestampTz ts)
     256             : {
     257        3702 :     PgStatShared_SLRU *stats_shmem = &pgStatLocal.shmem->slru;
     258             : 
     259        3702 :     LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
     260             : 
     261        3702 :     memset(&stats_shmem->stats[index], 0, sizeof(PgStat_SLRUStats));
     262        3702 :     stats_shmem->stats[index].stat_reset_timestamp = ts;
     263             : 
     264        3702 :     LWLockRelease(&stats_shmem->lock);
     265        3702 : }