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Commit1c2de47

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Remove BufferLocks[] array in favor of a single pointer to the buffer
(if any) currently waited for by LockBufferForCleanup(), which is allthat we were using it for anymore. Saves some space and eliminatesproportional-to-NBuffers slowdown in UnlockBuffers().
1 parent72f9013 commit1c2de47

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3 files changed

+35
-56
lines changed

3 files changed

+35
-56
lines changed

‎src/backend/storage/buffer/buf_init.c

Lines changed: 2 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/buffer/buf_init.c,v 1.68 2004/08/2905:06:47 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/buffer/buf_init.c,v 1.69 2004/10/16 18:05:06 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -20,9 +20,7 @@
2020

2121
BufferDesc*BufferDescriptors;
2222
Block*BufferBlockPointers;
23-
24-
int32*PrivateRefCount;/* also used in freelist.c */
25-
bits8*BufferLocks;/* flag bits showing locks I have set */
23+
int32*PrivateRefCount;
2624

2725
/* statistics counters */
2826
longintReadBufferCount;
@@ -177,7 +175,6 @@ InitBufferPoolAccess(void)
177175
sizeof(*BufferBlockPointers));
178176
PrivateRefCount= (int32*)calloc(NBuffers,
179177
sizeof(*PrivateRefCount));
180-
BufferLocks= (bits8*)calloc(NBuffers,sizeof(*BufferLocks));
181178

182179
/*
183180
* Convert shmem offsets into addresses as seen by this process. This

‎src/backend/storage/buffer/bufmgr.c

Lines changed: 31 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.178 2004/10/15 22:39:59 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.179 2004/10/16 18:05:06 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -66,6 +66,13 @@ longNDirectFileRead;/* some I/O's are direct file access.
6666
longNDirectFileWrite;/* e.g., I/O in psort and hashjoin. */
6767

6868

69+
/* local state for StartBufferIO and related functions */
70+
staticBufferDesc*InProgressBuf=NULL;
71+
staticboolIsForInput;
72+
/* local state for LockBufferForCleanup */
73+
staticBufferDesc*PinCountWaitBuf=NULL;
74+
75+
6976
staticvoidPinBuffer(BufferDesc*buf,boolfixOwner);
7077
staticvoidUnpinBuffer(BufferDesc*buf,boolfixOwner);
7178
staticvoidWaitIO(BufferDesc*buf);
@@ -1650,48 +1657,38 @@ SetBufferCommitInfoNeedsSave(Buffer buffer)
16501657
* Release buffer context locks for shared buffers.
16511658
*
16521659
* Used to clean up after errors.
1660+
*
1661+
* Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
1662+
* of releasing buffer context locks per se; the only thing we need to deal
1663+
* with here is clearing any PIN_COUNT request that was in progress.
16531664
*/
16541665
void
16551666
UnlockBuffers(void)
16561667
{
1657-
BufferDesc*buf;
1658-
inti;
1668+
BufferDesc*buf=PinCountWaitBuf;
16591669

1660-
for (i=0;i<NBuffers;i++)
1670+
if (buf)
16611671
{
1662-
bits8buflocks=BufferLocks[i];
1663-
1664-
if (buflocks==0)
1665-
continue;
1666-
1667-
buf=&(BufferDescriptors[i]);
1668-
16691672
HOLD_INTERRUPTS();/* don't want to die() partway through... */
16701673

1674+
LWLockAcquire(BufMgrLock,LW_EXCLUSIVE);
1675+
16711676
/*
1672-
* The buffer's cntx_lock has already been released by lwlock.c.
1677+
* Don't complain if flag bit not set; it could have been
1678+
* reset but we got a cancel/die interrupt before getting the
1679+
* signal.
16731680
*/
1681+
if ((buf->flags&BM_PIN_COUNT_WAITER)!=0&&
1682+
buf->wait_backend_id==MyBackendId)
1683+
buf->flags &= ~BM_PIN_COUNT_WAITER;
1684+
LWLockRelease(BufMgrLock);
16741685

1675-
if (buflocks&BL_PIN_COUNT_LOCK)
1676-
{
1677-
LWLockAcquire(BufMgrLock,LW_EXCLUSIVE);
1678-
1679-
/*
1680-
* Don't complain if flag bit not set; it could have been
1681-
* reset but we got a cancel/die interrupt before getting the
1682-
* signal.
1683-
*/
1684-
if ((buf->flags&BM_PIN_COUNT_WAITER)!=0&&
1685-
buf->wait_backend_id==MyBackendId)
1686-
buf->flags &= ~BM_PIN_COUNT_WAITER;
1687-
LWLockRelease(BufMgrLock);
1688-
ProcCancelWaitForSignal();
1689-
}
1690-
1691-
BufferLocks[i]=0;
1686+
ProcCancelWaitForSignal();
16921687

16931688
RESUME_INTERRUPTS();
16941689
}
1690+
1691+
PinCountWaitBuf=NULL;
16951692
}
16961693

16971694
/*
@@ -1779,9 +1776,9 @@ void
17791776
LockBufferForCleanup(Bufferbuffer)
17801777
{
17811778
BufferDesc*bufHdr;
1782-
bits8*buflock;
17831779

17841780
Assert(BufferIsValid(buffer));
1781+
Assert(PinCountWaitBuf==NULL);
17851782

17861783
if (BufferIsLocal(buffer))
17871784
{
@@ -1799,7 +1796,6 @@ LockBufferForCleanup(Buffer buffer)
17991796
PrivateRefCount[buffer-1]);
18001797

18011798
bufHdr=&BufferDescriptors[buffer-1];
1802-
buflock=&(BufferLocks[buffer-1]);
18031799

18041800
for (;;)
18051801
{
@@ -1822,24 +1818,22 @@ LockBufferForCleanup(Buffer buffer)
18221818
}
18231819
bufHdr->wait_backend_id=MyBackendId;
18241820
bufHdr->flags |=BM_PIN_COUNT_WAITER;
1825-
*buflock |=BL_PIN_COUNT_LOCK;
1821+
PinCountWaitBuf=bufHdr;
18261822
LWLockRelease(BufMgrLock);
18271823
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
18281824
/* Wait to be signaled by UnpinBuffer() */
18291825
ProcWaitForSignal();
1830-
*buflock &= ~BL_PIN_COUNT_LOCK;
1826+
PinCountWaitBuf=NULL;
18311827
/* Loop back and try again */
18321828
}
18331829
}
18341830

18351831
/*
18361832
*Functions for IO error handling
18371833
*
1838-
*Note: We assume that nested buffer IO neveroccur.
1834+
*Note: We assume that nested buffer IO neveroccurs.
18391835
*i.e at most one io_in_progress lock is held per proc.
1840-
*/
1841-
staticBufferDesc*InProgressBuf=NULL;
1842-
staticboolIsForInput;
1836+
*/
18431837

18441838
/*
18451839
* Function:StartBufferIO

‎src/include/storage/buf_internals.h

Lines changed: 2 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
99
* Portions Copyright (c) 1994, Regents of the University of California
1010
*
11-
* $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.73 2004/08/2905:06:58 momjian Exp $
11+
* $PostgreSQL: pgsql/src/include/storage/buf_internals.h,v 1.74 2004/10/16 18:05:07 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -75,8 +75,7 @@ typedef struct buftag
7575
)
7676

7777
/*
78-
*BufferDesc -- shared buffer cache metadata for a single
79-
* shared buffer descriptor.
78+
*BufferDesc -- shared descriptor/state data for a single shared buffer.
8079
*/
8180
typedefstructsbufdesc
8281
{
@@ -108,16 +107,6 @@ typedef struct sbufdesc
108107

109108
#defineBufferDescriptorGetBuffer(bdesc) ((bdesc)->buf_id + 1)
110109

111-
112-
/*
113-
* Each backend has its own BufferLocks[] array holding flag bits
114-
* showing what locks it has set on each buffer.
115-
*
116-
* We have to free these locks during ereport(ERROR)...
117-
*/
118-
#defineBL_IO_IN_PROGRESS(1 << 0)/* unimplemented */
119-
#defineBL_PIN_COUNT_LOCK(1 << 1)
120-
121110
/* entry for buffer lookup hashtable */
122111
typedefstruct
123112
{
@@ -206,7 +195,6 @@ extern void BufTableDelete(BufferTag *tagPtr);
206195

207196
/* bufmgr.c */
208197
externBufferDesc*BufferDescriptors;
209-
externbits8*BufferLocks;
210198

211199
/* localbuf.c */
212200
externBufferDesc*LocalBufferDescriptors;

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