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Refactor GetLockStatusData() to skip backends/groups without fast-path locks.

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Previously, GetLockStatusData() checked all slots for every backend
to gather fast-path lock data, which could be inefficient. This commit
refactors it by skipping backends with PID=0 (since they don't hold
fast-path locks) and skipping groups with no registered fast-path locks,
improving efficiency.

This refactoring is particularly beneficial, for example when
max_connections and max_locks_per_transaction are set high,
as it reduces unnecessary checks across numerous slots.

Author: Fujii Masao
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/a0a00c44-31e9-4c67-9846-fb9636213ac9@oss.nttdata.com
This commit is contained in:
Fujii Masao 2024-10-25 00:18:32 +09:00
parent 45188c2ea2
commit 86c30cef4a
1 changed files with 41 additions and 30 deletions
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71
src/backend/storage/lmgr/lock.c
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@ -3731,44 +3731,55 @@ GetLockStatusData(void)
for (i = 0; i < ProcGlobal->allProcCount; ++i) for (i = 0; i < ProcGlobal->allProcCount; ++i)
{ {
PGPROC *proc = &ProcGlobal->allProcs[i]; PGPROC *proc = &ProcGlobal->allProcs[i];
uint32 f;
/* Skip backends with pid=0, as they don't hold fast-path locks */
if (proc->pid == 0)
continue;
LWLockAcquire(&proc->fpInfoLock, LW_SHARED); LWLockAcquire(&proc->fpInfoLock, LW_SHARED);
for (f = 0; f < FP_LOCK_SLOTS_PER_BACKEND; ++f) for (uint32 g = 0; g < FastPathLockGroupsPerBackend; g++)
{ {
LockInstanceData *instance; /* Skip groups without registered fast-path locks */
uint32 lockbits = FAST_PATH_GET_BITS(proc, f); if (proc->fpLockBits[g] == 0)
/* Skip unallocated slots. */
if (!lockbits)
continue; continue;
if (el >= els) for (int j = 0; j < FP_LOCK_SLOTS_PER_GROUP; j++)
{ {
els += MaxBackends; LockInstanceData *instance;
data->locks = (LockInstanceData *) uint32 f = FAST_PATH_SLOT(g, j);
repalloc(data->locks, sizeof(LockInstanceData) * els); uint32 lockbits = FAST_PATH_GET_BITS(proc, f);
/* Skip unallocated slots */
if (!lockbits)
continue;
if (el >= els)
{
els += MaxBackends;
data->locks = (LockInstanceData *)
repalloc(data->locks, sizeof(LockInstanceData) * els);
}
instance = &data->locks[el];
SET_LOCKTAG_RELATION(instance->locktag, proc->databaseId,
proc->fpRelId[f]);
instance->holdMask = lockbits << FAST_PATH_LOCKNUMBER_OFFSET;
instance->waitLockMode = NoLock;
instance->vxid.procNumber = proc->vxid.procNumber;
instance->vxid.localTransactionId = proc->vxid.lxid;
instance->pid = proc->pid;
instance->leaderPid = proc->pid;
instance->fastpath = true;
/*
* Successfully taking fast path lock means there were no
* conflicting locks.
*/
instance->waitStart = 0;
el++;
} }
instance = &data->locks[el];
SET_LOCKTAG_RELATION(instance->locktag, proc->databaseId,
proc->fpRelId[f]);
instance->holdMask = lockbits << FAST_PATH_LOCKNUMBER_OFFSET;
instance->waitLockMode = NoLock;
instance->vxid.procNumber = proc->vxid.procNumber;
instance->vxid.localTransactionId = proc->vxid.lxid;
instance->pid = proc->pid;
instance->leaderPid = proc->pid;
instance->fastpath = true;
/*
* Successfully taking fast path lock means there were no
* conflicting locks.
*/
instance->waitStart = 0;
el++;
} }
if (proc->fpVXIDLock) if (proc->fpVXIDLock)