Instead of re-identifying which statistics bucket to use for a given
SLRU on every counter increment, do it once during shmem initialization.
This saves a fair number of cycles, and there's no real cost because
we could not have a bucket assignment that varies over time or across
backends anyway.
Also, get rid of the ill-considered decision to let pgstat.c pry
directly into SLRU's shared state; it's cleaner just to have slru.c
pass the stats bucket number.
In consequence of these changes, there's no longer any need to store
an SLRU's LWLock tranche info in shared memory, so get rid of that,
making this a net reduction in shmem consumption. (That partly
reverts
fe702a7b3.)
This is basically code review for
28cac71bd, so I also cleaned up
some comments, removed a dangling extern declaration, fixed some
things that should be static and/or const, etc.
Discussion: https://postgr.es/m/3618.
1589313035@sss.pgh.pa.us
/* shared->latest_page_number will be set later */
+ shared->slru_stats_idx = pgstat_slru_index(name);
+
ptr = (char *) shared;
offset = MAXALIGN(sizeof(SlruSharedData));
shared->page_buffer = (char **) (ptr + offset);
offset += MAXALIGN(nslots * nlsns * sizeof(XLogRecPtr));
}
- Assert(strlen(name) + 1 < SLRU_MAX_NAME_LENGTH);
- strlcpy(shared->lwlock_tranche_name, name, SLRU_MAX_NAME_LENGTH);
- shared->lwlock_tranche_id = tranche_id;
-
ptr += BUFFERALIGN(offset);
for (slotno = 0; slotno < nslots; slotno++)
{
LWLockInitialize(&shared->buffer_locks[slotno].lock,
- shared->lwlock_tranche_id);
+ tranche_id);
shared->page_buffer[slotno] = ptr;
shared->page_status[slotno] = SLRU_PAGE_EMPTY;
Assert(found);
/* Register SLRU tranche in the main tranches array */
- LWLockRegisterTranche(shared->lwlock_tranche_id,
- shared->lwlock_tranche_name);
+ LWLockRegisterTranche(tranche_id, name);
/*
* Initialize the unshared control struct, including directory path. We
shared->latest_page_number = pageno;
/* update the stats counter of zeroed pages */
- pgstat_count_slru_page_zeroed(ctl);
+ pgstat_count_slru_page_zeroed(shared->slru_stats_idx);
return slotno;
}
SlruRecentlyUsed(shared, slotno);
/* update the stats counter of pages found in the SLRU */
- pgstat_count_slru_page_hit(ctl);
+ pgstat_count_slru_page_hit(shared->slru_stats_idx);
return slotno;
}
SlruRecentlyUsed(shared, slotno);
/* update the stats counter of pages not found in SLRU */
- pgstat_count_slru_page_read(ctl);
+ pgstat_count_slru_page_read(shared->slru_stats_idx);
return slotno;
}
SlruRecentlyUsed(shared, slotno);
/* update the stats counter of pages found in the SLRU */
- pgstat_count_slru_page_hit(ctl);
+ pgstat_count_slru_page_hit(shared->slru_stats_idx);
return slotno;
}
off_t endpos;
/* update the stats counter of checked pages */
- pgstat_count_slru_page_exists(ctl);
+ pgstat_count_slru_page_exists(ctl->shared->slru_stats_idx);
SlruFileName(ctl, path, segno);
int fd = -1;
/* update the stats counter of written pages */
- pgstat_count_slru_page_written(ctl);
+ pgstat_count_slru_page_written(shared->slru_stats_idx);
/*
* Honor the write-WAL-before-data rule, if appropriate, so that we do not
bool ok;
/* update the stats counter of flushes */
- pgstat_count_slru_flush(ctl);
+ pgstat_count_slru_flush(shared->slru_stats_idx);
/*
* Find and write dirty pages
int slotno;
/* update the stats counter of truncates */
- pgstat_count_slru_truncate(ctl);
+ pgstat_count_slru_truncate(shared->slru_stats_idx);
/*
* The cutoff point is the start of the segment containing cutoffPage.
PgStat_MsgBgWriter BgWriterStats;
/*
- * SLRU statistics counters (unused in other processes) stored directly in
- * stats structure so it can be sent without needing to copy things around.
- * We assume this inits to zeroes. There is no central registry of SLRUs,
- * so we use this fixed list instead.
- *
- * There's a separte entry for each SLRU we have. The "other" entry is used
- * for all SLRUs without an explicit entry (e.g. SLRUs in extensions).
- */
-static char *slru_names[] = {"async", "clog", "commit_timestamp",
- "multixact_offset", "multixact_member",
- "oldserxid", "subtrans",
- "other" /* has to be last */};
+ * List of SLRU names that we keep stats for. There is no central registry of
+ * SLRUs, so we use this fixed list instead. The "other" entry is used for
+ * all SLRUs without an explicit entry (e.g. SLRUs in extensions).
+ */
+static const char *const slru_names[] = {
+ "async",
+ "clog",
+ "commit_timestamp",
+ "multixact_offset",
+ "multixact_member",
+ "oldserxid",
+ "subtrans",
+ "other" /* has to be last */
+};
+
+#define SLRU_NUM_ELEMENTS lengthof(slru_names)
-/* number of elemenents of slru_name array */
-#define SLRU_NUM_ELEMENTS (sizeof(slru_names) / sizeof(char *))
-
-/* entries in the same order as slru_names */
-PgStat_MsgSLRU SLRUStats[SLRU_NUM_ELEMENTS];
+/*
+ * SLRU statistics counts waiting to be sent to the collector. These are
+ * stored directly in stats message format so they can be sent without needing
+ * to copy things around. We assume this variable inits to zeroes. Entries
+ * are one-to-one with slru_names[].
+ */
+static PgStat_MsgSLRU SLRUStats[SLRU_NUM_ELEMENTS];
/* ----------
* Local data
static void
pgstat_send_slru(void)
{
- int i;
-
/* We assume this initializes to zeroes */
static const PgStat_MsgSLRU all_zeroes;
- for (i = 0; i < SLRU_NUM_ELEMENTS; i++)
+ for (int i = 0; i < SLRU_NUM_ELEMENTS; i++)
{
/*
* This function can be called even if nothing at all has happened. In
* in which case this returns NULL. This allows writing code that does not
* know the number of entries in advance.
*/
-char *
-pgstat_slru_name(int idx)
+const char *
+pgstat_slru_name(int slru_idx)
{
- Assert(idx >= 0);
-
- if (idx >= SLRU_NUM_ELEMENTS)
+ if (slru_idx < 0 || slru_idx >= SLRU_NUM_ELEMENTS)
return NULL;
- return slru_names[idx];
+ return slru_names[slru_idx];
}
/*
* Returns pointer to entry with counters for given SLRU (based on the name
* stored in SlruCtl as lwlock tranche name).
*/
-static PgStat_MsgSLRU *
-slru_entry(SlruCtl ctl)
+static inline PgStat_MsgSLRU *
+slru_entry(int slru_idx)
{
- int idx = pgstat_slru_index(ctl->shared->lwlock_tranche_name);
-
- Assert((idx >= 0) && (idx < SLRU_NUM_ELEMENTS));
+ Assert((slru_idx >= 0) && (slru_idx < SLRU_NUM_ELEMENTS));
- return &SLRUStats[idx];
+ return &SLRUStats[slru_idx];
}
+/*
+ * SLRU statistics count accumulation functions --- called from slru.c
+ */
+
void
-pgstat_count_slru_page_zeroed(SlruCtl ctl)
+pgstat_count_slru_page_zeroed(int slru_idx)
{
- slru_entry(ctl)->m_blocks_zeroed += 1;
+ slru_entry(slru_idx)->m_blocks_zeroed += 1;
}
void
-pgstat_count_slru_page_hit(SlruCtl ctl)
+pgstat_count_slru_page_hit(int slru_idx)
{
- slru_entry(ctl)->m_blocks_hit += 1;
+ slru_entry(slru_idx)->m_blocks_hit += 1;
}
void
-pgstat_count_slru_page_exists(SlruCtl ctl)
+pgstat_count_slru_page_exists(int slru_idx)
{
- slru_entry(ctl)->m_blocks_exists += 1;
+ slru_entry(slru_idx)->m_blocks_exists += 1;
}
void
-pgstat_count_slru_page_read(SlruCtl ctl)
+pgstat_count_slru_page_read(int slru_idx)
{
- slru_entry(ctl)->m_blocks_read += 1;
+ slru_entry(slru_idx)->m_blocks_read += 1;
}
void
-pgstat_count_slru_page_written(SlruCtl ctl)
+pgstat_count_slru_page_written(int slru_idx)
{
- slru_entry(ctl)->m_blocks_written += 1;
+ slru_entry(slru_idx)->m_blocks_written += 1;
}
void
-pgstat_count_slru_flush(SlruCtl ctl)
+pgstat_count_slru_flush(int slru_idx)
{
- slru_entry(ctl)->m_flush += 1;
+ slru_entry(slru_idx)->m_flush += 1;
}
void
-pgstat_count_slru_truncate(SlruCtl ctl)
+pgstat_count_slru_truncate(int slru_idx)
{
- slru_entry(ctl)->m_truncate += 1;
+ slru_entry(slru_idx)->m_truncate += 1;
}
Datum values[PG_STAT_GET_SLRU_COLS];
bool nulls[PG_STAT_GET_SLRU_COLS];
PgStat_SLRUStats stat = stats[i];
- char *name;
+ const char *name;
name = pgstat_slru_name(i);
*/
#define SLRU_PAGES_PER_SEGMENT 32
-/* Maximum length of an SLRU name */
-#define SLRU_MAX_NAME_LENGTH 32
-
/*
* Page status codes. Note that these do not include the "dirty" bit.
* page_dirty can be true only in the VALID or WRITE_IN_PROGRESS states;
bool *page_dirty;
int *page_number;
int *page_lru_count;
+ LWLockPadded *buffer_locks;
/*
* Optional array of WAL flush LSNs associated with entries in the SLRU
*/
int latest_page_number;
- /* LWLocks */
- int lwlock_tranche_id;
- char lwlock_tranche_name[SLRU_MAX_NAME_LENGTH];
- LWLockPadded *buffer_locks;
+ /* SLRU's index for statistics purposes (might not be unique) */
+ int slru_stats_idx;
} SlruSharedData;
typedef SlruSharedData *SlruShared;
#ifndef PGSTAT_H
#define PGSTAT_H
-#include "access/slru.h"
#include "datatype/timestamp.h"
#include "libpq/pqcomm.h"
#include "miscadmin.h"
} PgStat_MsgBgWriter;
/* ----------
- * PgStat_MsgSLRU Sent by the SLRU to update statistics.
+ * PgStat_MsgSLRU Sent by a backend to update SLRU statistics.
* ----------
*/
typedef struct PgStat_MsgSLRU
*/
extern PgStat_MsgBgWriter BgWriterStats;
-/*
- * SLRU statistics counters are updated directly by slru.
- */
-extern PgStat_MsgSLRU SlruStats[];
-
/*
* Updated by pgstat_count_buffer_*_time macros
*/
extern PgStat_GlobalStats *pgstat_fetch_global(void);
extern PgStat_SLRUStats *pgstat_fetch_slru(void);
-extern void pgstat_count_slru_page_zeroed(SlruCtl ctl);
-extern void pgstat_count_slru_page_hit(SlruCtl ctl);
-extern void pgstat_count_slru_page_read(SlruCtl ctl);
-extern void pgstat_count_slru_page_written(SlruCtl ctl);
-extern void pgstat_count_slru_page_exists(SlruCtl ctl);
-extern void pgstat_count_slru_flush(SlruCtl ctl);
-extern void pgstat_count_slru_truncate(SlruCtl ctl);
-extern char *pgstat_slru_name(int idx);
-extern int pgstat_slru_index(const char *name);
+extern void pgstat_count_slru_page_zeroed(int slru_idx);
+extern void pgstat_count_slru_page_hit(int slru_idx);
+extern void pgstat_count_slru_page_read(int slru_idx);
+extern void pgstat_count_slru_page_written(int slru_idx);
+extern void pgstat_count_slru_page_exists(int slru_idx);
+extern void pgstat_count_slru_flush(int slru_idx);
+extern void pgstat_count_slru_truncate(int slru_idx);
+extern const char *pgstat_slru_name(int slru_idx);
+extern int pgstat_slru_index(const char *name);
#endif /* PGSTAT_H */
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