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Create a "fast path" for acquiring weak relation locks.

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When an AccessShareLock, RowShareLock, or RowExclusiveLock is requested
on an unshared database relation, and we can verify that no conflicting
locks can possibly be present, record the lock in a per-backend queue,
stored within the PGPROC, rather than in the primary lock table.  This
eliminates a great deal of contention on the lock manager LWLocks.

This patch also refactors the interface between GetLockStatusData() and
pg_lock_status() to be a bit more abstract, so that we don't rely so
heavily on the lock manager's internal representation details.  The new
fast path lock structures don't have a LOCK or PROCLOCK structure to
return, so we mustn't depend on that for purposes of listing outstanding
locks.

Review by Jeff Davis.
This commit is contained in:
Robert Haas
2011-05-28 19:52:00 -04:00
parent 7ed8f6c517
commit 3cba8999b3
11 changed files with 1190 additions and 328 deletions
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87
src/backend/utils/adt/lockfuncs.c
View File

@ -49,6 +49,8 @@ typedef struct
int predLockIdx; /* current index for pred lock */
} PG_Lock_Status;
/* Number of columns in pg_locks output */
#define NUM_LOCK_STATUS_COLUMNS 15
/*
* VXIDGetDatum - Construct a text representation of a VXID
@ -96,7 +98,7 @@ pg_lock_status(PG_FUNCTION_ARGS)
/* build tupdesc for result tuples */
/* this had better match pg_locks view in system_views.sql */
tupdesc = CreateTemplateTupleDesc(14, false);
tupdesc = CreateTemplateTupleDesc(NUM_LOCK_STATUS_COLUMNS, false);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "locktype",
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "database",
@ -125,6 +127,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
TEXTOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 14, "granted",
BOOLOID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 15, "fastpath",
BOOLOID, -1, 0);
funcctx->tuple_desc = BlessTupleDesc(tupdesc);
@ -149,21 +153,17 @@ pg_lock_status(PG_FUNCTION_ARGS)
while (mystatus->currIdx < lockData->nelements)
{
PROCLOCK *proclock;
LOCK *lock;
PGPROC *proc;
bool granted;
LOCKMODE mode = 0;
const char *locktypename;
char tnbuf[32];
Datum values[14];
bool nulls[14];
Datum values[NUM_LOCK_STATUS_COLUMNS];
bool nulls[NUM_LOCK_STATUS_COLUMNS];
HeapTuple tuple;
Datum result;
LockInstanceData *instance;
proclock = &(lockData->proclocks[mystatus->currIdx]);
lock = &(lockData->locks[mystatus->currIdx]);
proc = &(lockData->procs[mystatus->currIdx]);
instance = &(lockData->locks[mystatus->currIdx]);
/*
* Look to see if there are any held lock modes in this PROCLOCK. If
@ -171,14 +171,14 @@ pg_lock_status(PG_FUNCTION_ARGS)
* again.
*/
granted = false;
if (proclock->holdMask)
if (instance->holdMask)
{
for (mode = 0; mode < MAX_LOCKMODES; mode++)
{
if (proclock->holdMask & LOCKBIT_ON(mode))
if (instance->holdMask & LOCKBIT_ON(mode))
{
granted = true;
proclock->holdMask &= LOCKBIT_OFF(mode);
instance->holdMask &= LOCKBIT_OFF(mode);
break;
}
}
@ -190,10 +190,10 @@ pg_lock_status(PG_FUNCTION_ARGS)
*/
if (!granted)
{
if (proc->waitLock == proclock->tag.myLock)
if (instance->waitLockMode != NoLock)
{
/* Yes, so report it with proper mode */
mode = proc->waitLockMode;
mode = instance->waitLockMode;
/*
* We are now done with this PROCLOCK, so advance pointer to
@ -218,22 +218,22 @@ pg_lock_status(PG_FUNCTION_ARGS)
MemSet(values, 0, sizeof(values));
MemSet(nulls, false, sizeof(nulls));
if (lock->tag.locktag_type <= LOCKTAG_LAST_TYPE)
locktypename = LockTagTypeNames[lock->tag.locktag_type];
if (instance->locktag.locktag_type <= LOCKTAG_LAST_TYPE)
locktypename = LockTagTypeNames[instance->locktag.locktag_type];
else
{
snprintf(tnbuf, sizeof(tnbuf), "unknown %d",
(int) lock->tag.locktag_type);
(int) instance->locktag.locktag_type);
locktypename = tnbuf;
}
values[0] = CStringGetTextDatum(locktypename);
switch ((LockTagType) lock->tag.locktag_type)
switch ((LockTagType) instance->locktag.locktag_type)
{
case LOCKTAG_RELATION:
case LOCKTAG_RELATION_EXTEND:
values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
values[2] = ObjectIdGetDatum(instance->locktag.locktag_field2);
nulls[3] = true;
nulls[4] = true;
nulls[5] = true;
@ -243,9 +243,9 @@ pg_lock_status(PG_FUNCTION_ARGS)
nulls[9] = true;
break;
case LOCKTAG_PAGE:
values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
values[3] = UInt32GetDatum(lock->tag.locktag_field3);
values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
values[2] = ObjectIdGetDatum(instance->locktag.locktag_field2);
values[3] = UInt32GetDatum(instance->locktag.locktag_field3);
nulls[4] = true;
nulls[5] = true;
nulls[6] = true;
@ -254,10 +254,10 @@ pg_lock_status(PG_FUNCTION_ARGS)
nulls[9] = true;
break;
case LOCKTAG_TUPLE:
values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
values[3] = UInt32GetDatum(lock->tag.locktag_field3);
values[4] = UInt16GetDatum(lock->tag.locktag_field4);
values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
values[2] = ObjectIdGetDatum(instance->locktag.locktag_field2);
values[3] = UInt32GetDatum(instance->locktag.locktag_field3);
values[4] = UInt16GetDatum(instance->locktag.locktag_field4);
nulls[5] = true;
nulls[6] = true;
nulls[7] = true;
@ -265,7 +265,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
nulls[9] = true;
break;
case LOCKTAG_TRANSACTION:
values[6] = TransactionIdGetDatum(lock->tag.locktag_field1);
values[6] =
TransactionIdGetDatum(instance->locktag.locktag_field1);
nulls[1] = true;
nulls[2] = true;
nulls[3] = true;
@ -276,8 +277,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
nulls[9] = true;
break;
case LOCKTAG_VIRTUALTRANSACTION:
values[5] = VXIDGetDatum(lock->tag.locktag_field1,
lock->tag.locktag_field2);
values[5] = VXIDGetDatum(instance->locktag.locktag_field1,
instance->locktag.locktag_field2);
nulls[1] = true;
nulls[2] = true;
nulls[3] = true;
@ -291,10 +292,10 @@ pg_lock_status(PG_FUNCTION_ARGS)
case LOCKTAG_USERLOCK:
case LOCKTAG_ADVISORY:
default: /* treat unknown locktags like OBJECT */
values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
values[7] = ObjectIdGetDatum(lock->tag.locktag_field2);
values[8] = ObjectIdGetDatum(lock->tag.locktag_field3);
values[9] = Int16GetDatum(lock->tag.locktag_field4);
values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
values[7] = ObjectIdGetDatum(instance->locktag.locktag_field2);
values[8] = ObjectIdGetDatum(instance->locktag.locktag_field3);
values[9] = Int16GetDatum(instance->locktag.locktag_field4);
nulls[2] = true;
nulls[3] = true;
nulls[4] = true;
@ -303,13 +304,14 @@ pg_lock_status(PG_FUNCTION_ARGS)
break;
}
values[10] = VXIDGetDatum(proc->backendId, proc->lxid);
if (proc->pid != 0)
values[11] = Int32GetDatum(proc->pid);
values[10] = VXIDGetDatum(instance->backend, instance->lxid);
if (instance->pid != 0)
values[11] = Int32GetDatum(instance->pid);
else
nulls[11] = true;
values[12] = CStringGetTextDatum(GetLockmodeName(LOCK_LOCKMETHOD(*lock), mode));
values[12] = CStringGetTextDatum(GetLockmodeName(instance->locktag.locktag_lockmethodid, mode));
values[13] = BoolGetDatum(granted);
values[14] = BoolGetDatum(instance->fastpath);
tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
result = HeapTupleGetDatum(tuple);
@ -327,8 +329,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
PREDICATELOCKTARGETTAG *predTag = &(predLockData->locktags[mystatus->predLockIdx]);
SERIALIZABLEXACT *xact = &(predLockData->xacts[mystatus->predLockIdx]);
Datum values[14];
bool nulls[14];
Datum values[NUM_LOCK_STATUS_COLUMNS];
bool nulls[NUM_LOCK_STATUS_COLUMNS];
HeapTuple tuple;
Datum result;
@ -374,11 +376,12 @@ pg_lock_status(PG_FUNCTION_ARGS)
nulls[11] = true;
/*
* Lock mode. Currently all predicate locks are SIReadLocks, which are
* always held (never waiting)
* Lock mode. Currently all predicate locks are SIReadLocks, which
* are always held (never waiting) and have no fast path
*/
values[12] = CStringGetTextDatum("SIReadLock");
values[13] = BoolGetDatum(true);
values[14] = BoolGetDatum(false);
tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
result = HeapTupleGetDatum(tuple);