Remove BufferLocks[] array in favor of a single pointer to the buffer

(if any) currently waited for by LockBufferForCleanup(), which is all
that we were using it for anymore.  Saves some space and eliminates
proportional-to-NBuffers slowdown in UnlockBuffers().

diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c
index 5b727c9a222b71ca3bb3e50ec5a39a6be8c4d2be..a0d7054623c9598ab265bbf484cf9f28cd0e7614 100644 (file)
--- a/src/backend/storage/buffer/buf_init.c
+++ b/src/backend/storage/buffer/buf_init.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/storage/buffer/buf_init.c,v 1.68 2004/08/29 05:06:47 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/storage/buffer/buf_init.c,v 1.69 2004/10/16 18:05:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -20,9 +20,7 @@
 
 BufferDesc *BufferDescriptors;
 Block     *BufferBlockPointers;
-
-int32     *PrivateRefCount;    /* also used in freelist.c */
-bits8     *BufferLocks;                /* flag bits showing locks I have set */
+int32     *PrivateRefCount;
 
 /* statistics counters */
 long int       ReadBufferCount;
@@ -177,7 +175,6 @@ InitBufferPoolAccess(void)
                                                                                   sizeof(*BufferBlockPointers));
        PrivateRefCount = (int32 *) calloc(NBuffers,
                                                                           sizeof(*PrivateRefCount));
-       BufferLocks = (bits8 *) calloc(NBuffers, sizeof(*BufferLocks));
 
        /*
         * Convert shmem offsets into addresses as seen by this process. This

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index a0f2bf9c117f981aa01fd779bb57a8299502d41d..a8cf506688fcd22f3e12390e489110008580d540 100644 (file)
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.178 2004/10/15 22:39:59 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.179 2004/10/16 18:05:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -66,6 +66,13 @@ long         NDirectFileRead;        /* some I/O's are direct file access.
 long           NDirectFileWrite;       /* e.g., I/O in psort and hashjoin. */
 
 
+/* local state for StartBufferIO and related functions */
+static BufferDesc *InProgressBuf = NULL;
+static bool IsForInput;
+/* local state for LockBufferForCleanup */
+static BufferDesc *PinCountWaitBuf = NULL;
+
+
 static void PinBuffer(BufferDesc *buf, bool fixOwner);
 static void UnpinBuffer(BufferDesc *buf, bool fixOwner);
 static void WaitIO(BufferDesc *buf);
@@ -1650,48 +1657,38 @@ SetBufferCommitInfoNeedsSave(Buffer buffer)
  * Release buffer context locks for shared buffers.
  *
  * Used to clean up after errors.
+ *
+ * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
+ * of releasing buffer context locks per se; the only thing we need to deal
+ * with here is clearing any PIN_COUNT request that was in progress.
  */
 void
 UnlockBuffers(void)
 {
-       BufferDesc *buf;
-       int                     i;
+       BufferDesc *buf = PinCountWaitBuf;
 
-       for (i = 0; i < NBuffers; i++)
+       if (buf)
        {
-               bits8           buflocks = BufferLocks[i];
-
-               if (buflocks == 0)
-                       continue;
-
-               buf = &(BufferDescriptors[i]);
-
                HOLD_INTERRUPTS();              /* don't want to die() partway through... */
 
+               LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
+
                /*
-                * The buffer's cntx_lock has already been released by lwlock.c.
+                * Don't complain if flag bit not set; it could have been
+                * reset but we got a cancel/die interrupt before getting the
+                * signal.
                 */
+               if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
+                       buf->wait_backend_id == MyBackendId)
+                       buf->flags &= ~BM_PIN_COUNT_WAITER;
+               LWLockRelease(BufMgrLock);
 
-               if (buflocks & BL_PIN_COUNT_LOCK)
-               {
-                       LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
-
-                       /*
-                        * Don't complain if flag bit not set; it could have been
-                        * reset but we got a cancel/die interrupt before getting the
-                        * signal.
-                        */
-                       if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
-                               buf->wait_backend_id == MyBackendId)
-                               buf->flags &= ~BM_PIN_COUNT_WAITER;
-                       LWLockRelease(BufMgrLock);
-                       ProcCancelWaitForSignal();
-               }
-
-               BufferLocks[i] = 0;
+               ProcCancelWaitForSignal();
 
                RESUME_INTERRUPTS();
        }
+
+       PinCountWaitBuf = NULL;
 }
 
 /*
@@ -1779,9 +1776,9 @@ void
 LockBufferForCleanup(Buffer buffer)
 {
        BufferDesc *bufHdr;
-       bits8      *buflock;
 
        Assert(BufferIsValid(buffer));
+       Assert(PinCountWaitBuf == NULL);
 
        if (BufferIsLocal(buffer))
        {
@@ -1799,7 +1796,6 @@ LockBufferForCleanup(Buffer buffer)
                         PrivateRefCount[buffer - 1]);
 
        bufHdr = &BufferDescriptors[buffer - 1];
-       buflock = &(BufferLocks[buffer - 1]);
 
        for (;;)
        {
@@ -1822,12 +1818,12 @@ LockBufferForCleanup(Buffer buffer)
                }
                bufHdr->wait_backend_id = MyBackendId;
                bufHdr->flags |= BM_PIN_COUNT_WAITER;
-               *buflock |= BL_PIN_COUNT_LOCK;
+               PinCountWaitBuf = bufHdr;
                LWLockRelease(BufMgrLock);
                LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
                /* Wait to be signaled by UnpinBuffer() */
                ProcWaitForSignal();
-               *buflock &= ~BL_PIN_COUNT_LOCK;
+               PinCountWaitBuf = NULL;
                /* Loop back and try again */
        }
 }
@@ -1835,11 +1831,9 @@ LockBufferForCleanup(Buffer buffer)
 /*
  *     Functions for IO error handling
  *
- *     Note : We assume that nested buffer IO never occur.
+ *     Note: We assume that nested buffer IO never occurs.
  *     i.e at most one io_in_progress lock is held per proc.
-*/
-static BufferDesc *InProgressBuf = NULL;
-static bool IsForInput;
+ */
 
 /*
  * Function:StartBufferIO

diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index 355859faa3baa4f35b3661032e2d3ff1f2d4c23b..857d26a22b48980ec6e37baa9d8a8be09bec0239 100644 (file)
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.73 2004/08/29 05:06:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.74 2004/10/16 18:05:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -75,8 +75,7 @@ typedef struct buftag
 )
 
 /*
- *     BufferDesc -- shared buffer cache metadata for a single
- *                               shared buffer descriptor.
+ *     BufferDesc -- shared descriptor/state data for a single shared buffer.
  */
 typedef struct sbufdesc
 {
@@ -108,16 +107,6 @@ typedef struct sbufdesc
 
 #define BufferDescriptorGetBuffer(bdesc) ((bdesc)->buf_id + 1)
 
-
-/*
- * Each backend has its own BufferLocks[] array holding flag bits
- * showing what locks it has set on each buffer.
- *
- * We have to free these locks during ereport(ERROR)...
- */
-#define BL_IO_IN_PROGRESS      (1 << 0)        /* unimplemented */
-#define BL_PIN_COUNT_LOCK      (1 << 1)
-
 /* entry for buffer lookup hashtable */
 typedef struct
 {
@@ -206,7 +195,6 @@ extern void BufTableDelete(BufferTag *tagPtr);
 
 /* bufmgr.c */
 extern BufferDesc *BufferDescriptors;
-extern bits8 *BufferLocks;
 
 /* localbuf.c */
 extern BufferDesc *LocalBufferDescriptors;