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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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5
src/backend/storage/lmgr/proc.c
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@ -67,7 +67,7 @@ PGPROC *MyProc = NULL;
NON_EXEC_STATIC slock_t *ProcStructLock = NULL;
/* Pointers to shared-memory structures */
NON_EXEC_STATIC PROC_HDR *ProcGlobal = NULL;
PROC_HDR *ProcGlobal = NULL;
NON_EXEC_STATIC PGPROC *AuxiliaryProcs = NULL;
/* If we are waiting for a lock, this points to the associated LOCALLOCK */
@ -183,6 +183,8 @@ InitProcGlobal(void)
* one of these purposes, and they do not move between groups.
*/
procs = (PGPROC *) ShmemAlloc(TotalProcs * sizeof(PGPROC));
ProcGlobal->allProcs = procs;
ProcGlobal->allProcCount = TotalProcs;
if (!procs)
ereport(FATAL,
(errcode(ERRCODE_OUT_OF_MEMORY),
@ -192,6 +194,7 @@ InitProcGlobal(void)
{
/* Common initialization for all PGPROCs, regardless of type. */
PGSemaphoreCreate(&(procs[i].sem));
procs[i].backendLock = LWLockAssign();
InitSharedLatch(&procs[i].waitLatch);
/*