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Marginal performance improvement in LockBuffer --- calculate address 

of BufferLocks[] entry just once.  Seems to save 10% or so of the
routine's runtime, which'd not be worth worrying about if it weren't
such a hotspot.
This commit is contained in:
Tom Lane 2000-03-14 22:46:27 +00:00
parent e02cde4b0a
commit c40a0a1b52
1 changed files with 19 additions and 17 deletions
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36
src/backend/storage/buffer/bufmgr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.75 2000/02/21 18:49:00 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/bufmgr.c,v 1.76 2000/03/14 22:46:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -2072,12 +2072,14 @@ void
LockBuffer(Buffer buffer, int mode)
{
BufferDesc *buf;
bits8 *buflock;
Assert(BufferIsValid(buffer));
if (BufferIsLocal(buffer))
return;
buf = &(BufferDescriptors[buffer - 1]);
buflock = &(BufferLocks[buffer - 1]);
#ifdef HAS_TEST_AND_SET
S_LOCK(&(buf->cntx_lock));
@ -2087,21 +2089,21 @@ LockBuffer(Buffer buffer, int mode)
if (mode == BUFFER_LOCK_UNLOCK)
{
if (BufferLocks[buffer - 1] & BL_R_LOCK)
if (*buflock & BL_R_LOCK)
{
Assert(buf->r_locks > 0);
Assert(!(buf->w_lock));
Assert(!(BufferLocks[buffer - 1] & (BL_W_LOCK | BL_RI_LOCK)))
(buf->r_locks)--;
BufferLocks[buffer - 1] &= ~BL_R_LOCK;
Assert(!(*buflock & (BL_W_LOCK | BL_RI_LOCK)));
(buf->r_locks)--;
*buflock &= ~BL_R_LOCK;
}
else if (BufferLocks[buffer - 1] & BL_W_LOCK)
else if (*buflock & BL_W_LOCK)
{
Assert(buf->w_lock);
Assert(buf->r_locks == 0);
Assert(!(BufferLocks[buffer - 1] & (BL_R_LOCK | BL_RI_LOCK)))
buf->w_lock = false;
BufferLocks[buffer - 1] &= ~BL_W_LOCK;
Assert(!(*buflock & (BL_R_LOCK | BL_RI_LOCK)));
buf->w_lock = false;
*buflock &= ~BL_W_LOCK;
}
else
elog(ERROR, "UNLockBuffer: buffer %lu is not locked", buffer);
@ -2110,7 +2112,7 @@ LockBuffer(Buffer buffer, int mode)
{
unsigned i = 0;
Assert(!(BufferLocks[buffer - 1] & (BL_R_LOCK | BL_W_LOCK | BL_RI_LOCK)));
Assert(!(*buflock & (BL_R_LOCK | BL_W_LOCK | BL_RI_LOCK)));
while (buf->ri_lock || buf->w_lock)
{
#ifdef HAS_TEST_AND_SET
@ -2124,16 +2126,16 @@ LockBuffer(Buffer buffer, int mode)
#endif
}
(buf->r_locks)++;
BufferLocks[buffer - 1] |= BL_R_LOCK;
*buflock |= BL_R_LOCK;
}
else if (mode == BUFFER_LOCK_EXCLUSIVE)
{
unsigned i = 0;
Assert(!(BufferLocks[buffer - 1] & (BL_R_LOCK | BL_W_LOCK | BL_RI_LOCK)));
Assert(!(*buflock & (BL_R_LOCK | BL_W_LOCK | BL_RI_LOCK)));
while (buf->r_locks > 0 || buf->w_lock)
{
if (buf->r_locks > 3 || (BufferLocks[buffer - 1] & BL_RI_LOCK))
if (buf->r_locks > 3 || (*buflock & BL_RI_LOCK))
{
/*
* Our RI lock might be removed by concurrent W lock
@ -2141,7 +2143,7 @@ LockBuffer(Buffer buffer, int mode)
* when our own W acquiring succeeded) and so
* we set RI lock again if we already did this.
*/
BufferLocks[buffer - 1] |= BL_RI_LOCK;
*buflock |= BL_RI_LOCK;
buf->ri_lock = true;
}
#ifdef HAS_TEST_AND_SET
@ -2155,15 +2157,15 @@ LockBuffer(Buffer buffer, int mode)
#endif
}
buf->w_lock = true;
BufferLocks[buffer - 1] |= BL_W_LOCK;
if (BufferLocks[buffer - 1] & BL_RI_LOCK)
*buflock |= BL_W_LOCK;
if (*buflock & BL_RI_LOCK)
{
/*
* It's possible to remove RI locks acquired by another
* W lockers here, but they'll take care about it.
*/
buf->ri_lock = false;
BufferLocks[buffer - 1] &= ~BL_RI_LOCK;
*buflock &= ~BL_RI_LOCK;
}
}
else