Yes, I pushed the document_overhead_by_track_planning.patch, but this
CF entry is for pgss_lwlock_v1.patch which replaces spinlocks with lwlocks
in pg_stat_statements. The latter patch has not been committed yet.
Probably attachding the different patches in the same thread would cause
this confusing thing... Anyway, thanks for your comment!
To avoid further confusion, I attached the rebased version of
the patch that was registered at CF. I'd appreciate it if
you review this version.
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c
b/contrib/pg_stat_statements/pg_stat_statements.c
index 6b91c62c31..3035c14ed5 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -39,7 +39,7 @@
* in an entry except the counters requires the same. To look up an entry,
* one must hold the lock shared. To read or update the counters within
* an entry, one must hold the lock shared or exclusive (so the entry doesn't
- * disappear!) and also take the entry's mutex spinlock.
+ * disappear!) and also take the entry's partition lock.
* The shared state variable pgss->extent (the next free spot in the external
* query-text file) should be accessed only while holding either the
* pgss->mutex spinlock, or exclusive lock on pgss->lock. We use the mutex to
@@ -115,6 +115,11 @@ static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM
/ 100;
#define JUMBLE_SIZE 1024 /* query serialization
buffer size */
+#define PGSS_NUM_LOCK_PARTITIONS() (pgss_max)
+#define PGSS_HASH_PARTITION_LOCK(key) \
+ (&(pgss->base + \
+ (get_hash_value(pgss_hash, key) % PGSS_NUM_LOCK_PARTITIONS()))->lock)
+
/*
* Extension version number, for supporting older extension versions' objects
*/
@@ -207,7 +212,7 @@ typedef struct pgssEntry
Size query_offset; /* query text offset in external file */
int query_len; /* # of valid bytes in
query string, or -1 */
int encoding; /* query text encoding
*/
- slock_t mutex; /* protects the counters only */
+ LWLock *lock; /* protects the counters only */
} pgssEntry;
/*
@@ -216,6 +221,7 @@ typedef struct pgssEntry
typedef struct pgssSharedState
{
LWLock *lock; /* protects hashtable
search/modification */
+ LWLockPadded *base; /* base address of this LWLock */
double cur_median_usage; /* current median usage in
hashtable */
Size mean_query_len; /* current mean entry text length */
slock_t mutex; /* protects following fields
only: */
@@ -468,7 +474,8 @@ _PG_init(void)
* resources in pgss_shmem_startup().
*/
RequestAddinShmemSpace(pgss_memsize());
- RequestNamedLWLockTranche("pg_stat_statements", 1);
+ RequestNamedLWLockTranche("pg_stat_statements",
+
PGSS_NUM_LOCK_PARTITIONS() + 1);
/*
* Install hooks.
@@ -547,7 +554,8 @@ pgss_shmem_startup(void)
if (!found)
{
/* First time through ... */
- pgss->lock =
&(GetNamedLWLockTranche("pg_stat_statements"))->lock;
+ pgss->base = GetNamedLWLockTranche("pg_stat_statements");
+ pgss->lock = &(pgss->base + pgss_max)->lock;
pgss->cur_median_usage = ASSUMED_MEDIAN_INIT;
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
SpinLockInit(&pgss->mutex);
@@ -1384,14 +1392,14 @@ pgss_store(const char *query, uint64 queryId,
if (!jstate)
{
/*
- * Grab the spinlock while updating the counters (see comment
about
- * locking rules at the head of the file)
+ * Grab the partition lock while updating the counters (see
comment
+ * about locking rules at the head of the file)
*/
volatile pgssEntry *e = (volatile pgssEntry *) entry;
Assert(kind == PGSS_PLAN || kind == PGSS_EXEC);
- SpinLockAcquire(&e->mutex);
+ LWLockAcquire(e->lock, LW_EXCLUSIVE);
/* "Unstick" entry if it was previously sticky */
if (IS_STICKY(e->counters))
@@ -1443,7 +1451,7 @@ pgss_store(const char *query, uint64 queryId,
e->counters.wal_fpi += walusage->wal_fpi;
e->counters.wal_bytes += walusage->wal_bytes;
- SpinLockRelease(&e->mutex);
+ LWLockRelease(e->lock);
}
done:
@@ -1770,9 +1778,9 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
{
volatile pgssEntry *e = (volatile pgssEntry *) entry;
- SpinLockAcquire(&e->mutex);
+ LWLockAcquire(e->lock, LW_SHARED);
tmp = e->counters;
- SpinLockRelease(&e->mutex);
+ LWLockRelease(e->lock);
}
/* Skip entry if unexecuted (ie, it's a pending "sticky" entry)
*/
@@ -1916,8 +1924,8 @@ entry_alloc(pgssHashKey *key, Size query_offset, int
query_len, int encoding,
memset(&entry->counters, 0, sizeof(Counters));
/* set the appropriate initial usage count */
entry->counters.usage = sticky ? pgss->cur_median_usage :
USAGE_INIT;
- /* re-initialize the mutex each time ... we assume no one using
it */
- SpinLockInit(&entry->mutex);
+ /* determine which partition lock to use for this query */
+ entry->lock = PGSS_HASH_PARTITION_LOCK(key);
/* ... and don't forget the query text metadata */
Assert(query_len >= 0);
entry->query_offset = query_offset;
