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Commit3ae7e4a

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Remove BufferBlockPointers array in favor of a base + (bufnum) * BLCKSZ
computation. On modern machines this is as fast if not faster, and wedon't have to clog the CPU's L2 cache with a tens-of-KB pointer array.If we ever decide to adopt a more dynamic allocation method for sharedbuffers, we'll probably have to revert this patch, but in the meantimewe might as well save a few bytes and nanoseconds. Per Qingqing Zhou.
1 parentb609695 commit3ae7e4a

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3 files changed

+7
-28
lines changed

3 files changed

+7
-28
lines changed

‎src/backend/storage/buffer/buf_init.c

Lines changed: 2 additions & 23 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 1.74 2005/08/08 03:11:44 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/buffer/buf_init.c,v 1.75 2005/08/12 05:05:50 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -19,11 +19,9 @@
1919

2020

2121
BufferDesc*BufferDescriptors;
22-
Block*BufferBlockPointers;
22+
char*BufferBlocks;
2323
int32*PrivateRefCount;
2424

25-
staticchar*BufferBlocks;
26-
2725
/* statistics counters */
2826
longintReadBufferCount;
2927
longintReadLocalBufferCount;
@@ -154,30 +152,11 @@ InitBufferPool(void)
154152
void
155153
InitBufferPoolAccess(void)
156154
{
157-
char*block;
158-
inti;
159-
160155
/*
161156
* Allocate and zero local arrays of per-buffer info.
162157
*/
163-
BufferBlockPointers= (Block*)calloc(NBuffers,
164-
sizeof(*BufferBlockPointers));
165158
PrivateRefCount= (int32*)calloc(NBuffers,
166159
sizeof(*PrivateRefCount));
167-
168-
/*
169-
* Construct addresses for the individual buffer data blocks. We do
170-
* this just to speed up the BufferGetBlock() macro. (Since the
171-
* addresses should be the same in every backend, we could inherit
172-
* this data from the postmaster --- but in the EXEC_BACKEND case
173-
* that doesn't work.)
174-
*/
175-
block=BufferBlocks;
176-
for (i=0;i<NBuffers;i++)
177-
{
178-
BufferBlockPointers[i]= (Block)block;
179-
block+=BLCKSZ;
180-
}
181160
}
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183162
/*

‎src/backend/storage/buffer/bufmgr.c

Lines changed: 2 additions & 2 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 1.192 2005/08/08 19:44:22 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.193 2005/08/12 05:05:50 tgl Exp $
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*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -54,7 +54,7 @@
5454

5555

5656
/* Note: these two macros only work on shared buffers, not local ones! */
57-
#defineBufHdrGetBlock(bufHdr)BufferBlockPointers[(bufHdr)->buf_id]
57+
#defineBufHdrGetBlock(bufHdr)((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
5858
#defineBufferGetLSN(bufHdr)(*((XLogRecPtr*) BufHdrGetBlock(bufHdr)))
5959

6060
/* Note: this macro only works on local buffers, not shared ones! */

‎src/include/storage/bufmgr.h

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.94 2005/08/08 03:12:16 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.95 2005/08/12 05:05:51 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -33,7 +33,7 @@ extern intbgwriter_lru_maxpages;
3333
externintbgwriter_all_maxpages;
3434

3535
/* in buf_init.c */
36-
externDLLIMPORTBlock*BufferBlockPointers;
36+
externDLLIMPORTchar*BufferBlocks;
3737
externDLLIMPORTint32*PrivateRefCount;
3838

3939
/* in localbuf.c */
@@ -107,7 +107,7 @@ extern DLLIMPORT int32 *LocalRefCount;
107107
BufferIsLocal(buffer) ? \
108108
LocalBufferBlockPointers[-(buffer) - 1] \
109109
: \
110-
BufferBlockPointers[(buffer) - 1] \
110+
(Block) (BufferBlocks + ((Size) ((buffer) - 1)) * BLCKSZ) \
111111
)
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113113
/*

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