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Simplify coding in slru.c 

New code in 53c2a97a92 uses direct array access to
shared->bank_locks[bankno].lock which can be made a little bit more
legible by using the SimpleLruGetBankLock helper function.
Nothing terribly serious, but let's add some clarity.

Discussion: https://postgr.es/m/202403041517.3a35jw53os65@alvherre.pgsql
This commit is contained in:
Alvaro Herrera 2024-03-04 17:37:47 +01:00
parent c8a61e350d
commit f9baaf96d3
No known key found for this signature in database
GPG Key ID: 1C20ACB9D5C564AE
1 changed files with 9 additions and 9 deletions
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18
src/backend/access/transam/slru.c
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@ -489,14 +489,14 @@ SimpleLruReadPage(SlruCtl ctl, int64 pageno, bool write_ok,
TransactionId xid)
{
SlruShared shared = ctl->shared;
LWLock *banklock = SimpleLruGetBankLock(ctl, pageno);
Assert(LWLockHeldByMeInMode(SimpleLruGetBankLock(ctl, pageno), LW_EXCLUSIVE));
Assert(LWLockHeldByMeInMode(banklock, LW_EXCLUSIVE));
/* Outer loop handles restart if we must wait for someone else's I/O */
for (;;)
{
int slotno;
int bankno;
bool ok;
/* See if page already is in memory; if not, pick victim slot */
@ -539,10 +539,9 @@ SimpleLruReadPage(SlruCtl ctl, int64 pageno, bool write_ok,
/* Acquire per-buffer lock (cannot deadlock, see notes at top) */
LWLockAcquire(&shared->buffer_locks[slotno].lock, LW_EXCLUSIVE);
bankno = SlotGetBankNumber(slotno);
/* Release bank lock while doing I/O */
LWLockRelease(&shared->bank_locks[bankno].lock);
LWLockRelease(banklock);
/* Do the read */
ok = SlruPhysicalReadPage(ctl, pageno, slotno);
@ -551,7 +550,7 @@ SimpleLruReadPage(SlruCtl ctl, int64 pageno, bool write_ok,
SimpleLruZeroLSNs(ctl, slotno);
/* Re-acquire bank control lock and update page state */
LWLockAcquire(&shared->bank_locks[bankno].lock, LW_EXCLUSIVE);
LWLockAcquire(banklock, LW_EXCLUSIVE);
Assert(shared->page_number[slotno] == pageno &&
shared->page_status[slotno] == SLRU_PAGE_READ_IN_PROGRESS &&
@ -592,12 +591,13 @@ int
SimpleLruReadPage_ReadOnly(SlruCtl ctl, int64 pageno, TransactionId xid)
{
SlruShared shared = ctl->shared;
LWLock *banklock = SimpleLruGetBankLock(ctl, pageno);
int bankno = pageno & ctl->bank_mask;
int bankstart = bankno * SLRU_BANK_SIZE;
int bankend = bankstart + SLRU_BANK_SIZE;
/* Try to find the page while holding only shared lock */
LWLockAcquire(&shared->bank_locks[bankno].lock, LW_SHARED);
LWLockAcquire(banklock, LW_SHARED);
/* See if page is already in a buffer */
for (int slotno = bankstart; slotno < bankend; slotno++)
@ -617,8 +617,8 @@ SimpleLruReadPage_ReadOnly(SlruCtl ctl, int64 pageno, TransactionId xid)
}
/* No luck, so switch to normal exclusive lock and do regular read */
LWLockRelease(&shared->bank_locks[bankno].lock);
LWLockAcquire(&shared->bank_locks[bankno].lock, LW_EXCLUSIVE);
LWLockRelease(banklock);
LWLockAcquire(banklock, LW_EXCLUSIVE);
return SimpleLruReadPage(ctl, pageno, true, xid);
}
@ -1167,7 +1167,7 @@ SlruSelectLRUPage(SlruCtl ctl, int64 pageno)
int bankstart = bankno * SLRU_BANK_SIZE;
int bankend = bankstart + SLRU_BANK_SIZE;
Assert(LWLockHeldByMe(&shared->bank_locks[bankno].lock));
Assert(LWLockHeldByMe(SimpleLruGetBankLock(ctl, pageno)));
/* See if page already has a buffer assigned */
for (int slotno = 0; slotno < shared->num_slots; slotno++)