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.

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index d1bcf40923cbdfd7f492a61dc6dad6e8a4cbc786..74378e9ea72575d91bb6ea1af50f5eb5df266139 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -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