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) 2001-2026, 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 3 : pgstat_reset_slru(const char *name)
46 : {
47 3 : TimestampTz ts = GetCurrentTimestamp();
48 :
49 : Assert(name != NULL);
50 :
51 3 : pgstat_reset_slru_counter_internal(pgstat_get_slru_index(name), ts);
52 3 : }
53 :
54 : /*
55 : * SLRU statistics count accumulation functions --- called from slru.c
56 : */
57 :
58 : #define PGSTAT_COUNT_SLRU(stat) \
59 : void \
60 : CppConcat(pgstat_count_slru_,stat)(int slru_idx) \
61 : { \
62 : get_slru_entry(slru_idx)->stat += 1; \
63 : }
64 :
65 : /* pgstat_count_slru_blocks_zeroed */
66 7345840 : PGSTAT_COUNT_SLRU(blocks_zeroed)
67 :
68 : /* pgstat_count_slru_blocks_hit */
69 1138027 : PGSTAT_COUNT_SLRU(blocks_hit)
70 :
71 : /* pgstat_count_slru_blocks_exists */
72 67 : PGSTAT_COUNT_SLRU(blocks_exists)
73 :
74 : /* pgstat_count_slru_blocks_read */
75 17601 : PGSTAT_COUNT_SLRU(blocks_read)
76 :
77 : /* pgstat_count_slru_blocks_written */
78 7346541 : PGSTAT_COUNT_SLRU(blocks_written)
79 :
80 : /* pgstat_count_slru_flush */
81 9087 : PGSTAT_COUNT_SLRU(flush)
82 :
83 : /* pgstat_count_slru_truncate */
84 1882 : PGSTAT_COUNT_SLRU(truncate)
85 :
86 : /*
87 : * Support function for the SQL-callable pgstat* functions. Returns
88 : * a pointer to the slru statistics struct.
89 : */
90 : PgStat_SLRUStats *
91 62 : pgstat_fetch_slru(void)
92 : {
93 62 : pgstat_snapshot_fixed(PGSTAT_KIND_SLRU);
94 :
95 62 : return pgStatLocal.snapshot.slru;
96 : }
97 :
98 : /*
99 : * Returns SLRU name for an index. The index may be above SLRU_NUM_ELEMENTS,
100 : * in which case this returns NULL. This allows writing code that does not
101 : * know the number of entries in advance.
102 : */
103 : const char *
104 558 : pgstat_get_slru_name(int slru_idx)
105 : {
106 558 : if (slru_idx < 0 || slru_idx >= SLRU_NUM_ELEMENTS)
107 62 : return NULL;
108 :
109 496 : return slru_names[slru_idx];
110 : }
111 :
112 : /*
113 : * Determine index of entry for a SLRU with a given name. If there's no exact
114 : * match, returns index of the last "other" entry used for SLRUs defined in
115 : * external projects.
116 : */
117 : int
118 8113 : pgstat_get_slru_index(const char *name)
119 : {
120 : int i;
121 :
122 32463 : for (i = 0; i < SLRU_NUM_ELEMENTS; i++)
123 : {
124 32459 : if (strcmp(slru_names[i], name) == 0)
125 8109 : return i;
126 : }
127 :
128 : /* return index of the last entry (which is the "other" one) */
129 4 : return (SLRU_NUM_ELEMENTS - 1);
130 : }
131 :
132 : /*
133 : * Flush out locally pending SLRU stats entries
134 : *
135 : * If nowait is true, this function returns false on lock failure. Otherwise
136 : * this function always returns true.
137 : *
138 : * If nowait is true, this function returns true if the lock could not be
139 : * acquired. Otherwise return false.
140 : */
141 : bool
142 37376 : pgstat_slru_flush_cb(bool nowait)
143 : {
144 37376 : PgStatShared_SLRU *stats_shmem = &pgStatLocal.shmem->slru;
145 : int i;
146 :
147 37376 : if (!have_slrustats)
148 23300 : return false;
149 :
150 14076 : if (!nowait)
151 11168 : LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
152 2908 : else if (!LWLockConditionalAcquire(&stats_shmem->lock, LW_EXCLUSIVE))
153 0 : return true;
154 :
155 126684 : for (i = 0; i < SLRU_NUM_ELEMENTS; i++)
156 : {
157 112608 : PgStat_SLRUStats *sharedent = &stats_shmem->stats[i];
158 112608 : PgStat_SLRUStats *pendingent = &pending_SLRUStats[i];
159 :
160 : #define SLRU_ACC(fld) sharedent->fld += pendingent->fld
161 112608 : SLRU_ACC(blocks_zeroed);
162 112608 : SLRU_ACC(blocks_hit);
163 112608 : SLRU_ACC(blocks_read);
164 112608 : SLRU_ACC(blocks_written);
165 112608 : SLRU_ACC(blocks_exists);
166 112608 : SLRU_ACC(flush);
167 112608 : SLRU_ACC(truncate);
168 : #undef SLRU_ACC
169 : }
170 :
171 : /* done, clear the pending entry */
172 914940 : MemSet(pending_SLRUStats, 0, sizeof(pending_SLRUStats));
173 :
174 14076 : LWLockRelease(&stats_shmem->lock);
175 :
176 14076 : have_slrustats = false;
177 :
178 14076 : return false;
179 : }
180 :
181 : void
182 1158 : pgstat_slru_init_shmem_cb(void *stats)
183 : {
184 1158 : PgStatShared_SLRU *stats_shmem = (PgStatShared_SLRU *) stats;
185 :
186 1158 : LWLockInitialize(&stats_shmem->lock, LWTRANCHE_PGSTATS_DATA);
187 1158 : }
188 :
189 : void
190 245 : pgstat_slru_reset_all_cb(TimestampTz ts)
191 : {
192 2205 : for (int i = 0; i < SLRU_NUM_ELEMENTS; i++)
193 1960 : pgstat_reset_slru_counter_internal(i, ts);
194 245 : }
195 :
196 : void
197 772 : pgstat_slru_snapshot_cb(void)
198 : {
199 772 : PgStatShared_SLRU *stats_shmem = &pgStatLocal.shmem->slru;
200 :
201 772 : LWLockAcquire(&stats_shmem->lock, LW_SHARED);
202 :
203 772 : memcpy(pgStatLocal.snapshot.slru, &stats_shmem->stats,
204 : sizeof(stats_shmem->stats));
205 :
206 772 : LWLockRelease(&stats_shmem->lock);
207 772 : }
208 :
209 : /*
210 : * Returns pointer to entry with counters for given SLRU (based on the name
211 : * stored in SlruCtl as lwlock tranche name).
212 : */
213 : static inline PgStat_SLRUStats *
214 15859045 : get_slru_entry(int slru_idx)
215 : {
216 : pgstat_assert_is_up();
217 :
218 : /*
219 : * The postmaster should never register any SLRU statistics counts; if it
220 : * did, the counts would be duplicated into child processes via fork().
221 : */
222 : Assert(IsUnderPostmaster || !IsPostmasterEnvironment);
223 :
224 : Assert((slru_idx >= 0) && (slru_idx < SLRU_NUM_ELEMENTS));
225 :
226 15859045 : have_slrustats = true;
227 15859045 : pgstat_report_fixed = true;
228 :
229 15859045 : return &pending_SLRUStats[slru_idx];
230 : }
231 :
232 : static void
233 1963 : pgstat_reset_slru_counter_internal(int index, TimestampTz ts)
234 : {
235 1963 : PgStatShared_SLRU *stats_shmem = &pgStatLocal.shmem->slru;
236 :
237 1963 : LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
238 :
239 1963 : memset(&stats_shmem->stats[index], 0, sizeof(PgStat_SLRUStats));
240 1963 : stats_shmem->stats[index].stat_reset_timestamp = ts;
241 :
242 1963 : LWLockRelease(&stats_shmem->lock);
243 1963 : }
|
