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Commit3a246cc

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committed
Arrange to preallocate all required space for the buffer and FSM hash
tables in shared memory. This ensures that overflow of the lock tablecreates no long-lasting problems. Per discussion with Merlin Moncure.
1 parentd9b68c8 commit3a246cc

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6 files changed

+42
-18
lines changed

6 files changed

+42
-18
lines changed

‎src/backend/storage/freespace/freespace.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/freespace/freespace.c,v 1.34 2004/08/29 05:06:47 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/freespace/freespace.c,v 1.35 2004/09/28 20:46:27 tgl Exp $
1212
*
1313
*
1414
* NOTES:
@@ -283,8 +283,8 @@ InitFreeSpaceMap(void)
283283
info.hash=tag_hash;
284284

285285
FreeSpaceMapRelHash=ShmemInitHash("Free Space Map Hash",
286-
MaxFSMRelations/10,
287-
MaxFSMRelations,
286+
MaxFSMRelations+1,
287+
MaxFSMRelations+1,
288288
&info,
289289
(HASH_ELEM |HASH_FUNCTION));
290290

‎src/backend/storage/ipc/shmem.c

Lines changed: 11 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/ipc/shmem.c,v 1.80 2004/08/29 05:06:48 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/ipc/shmem.c,v 1.81 2004/09/28 20:46:29 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -262,8 +262,17 @@ InitShmemIndex(void)
262262
*shared memory hash table.
263263
*
264264
* We assume caller is doing some kind of synchronization
265-
* so that two peopledont try to create/initialize the
265+
* so that two peopledon't try to create/initialize the
266266
* table at once.
267+
*
268+
* max_size is the estimated maximum number of hashtable entries. This is
269+
* not a hard limit, but the access efficiency will degrade if it is
270+
* exceeded substantially (since it's used to compute directory size and
271+
* the hash table buckets will get overfull).
272+
*
273+
* init_size is the number of hashtable entries to preallocate. For a table
274+
* whose maximum size is certain, this should be equal to max_size; that
275+
* ensures that no run-time out-of-shared-memory failures can occur.
267276
*/
268277
HTAB*
269278
ShmemInitHash(constchar*name,/* table string name for shmem index */

‎src/backend/storage/lmgr/lock.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/lmgr/lock.c,v 1.140 2004/09/12 18:30:50 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.141 2004/09/28 20:46:32 tgl Exp $
1212
*
1313
* NOTES
1414
* Outside modules can create a lock table and acquire/release
@@ -241,7 +241,7 @@ LockMethodTableInit(const char *tabName,
241241

242242
/* Compute init/max size to request for lock hashtables */
243243
max_table_size=NLOCKENTS(maxBackends);
244-
init_table_size=max_table_size /10;
244+
init_table_size=max_table_size /2;
245245

246246
/* Allocate a string for the shmem index table lookups. */
247247
/* This is just temp space in this routine, so palloc is OK. */

‎src/backend/utils/hash/dynahash.c

Lines changed: 21 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.53 2004/08/29 05:06:50 momjian Exp $
12+
* $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.54 2004/09/28 20:46:34 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -63,7 +63,7 @@
6363
*/
6464
staticvoid*DynaHashAlloc(Sizesize);
6565
staticHASHSEGMENTseg_alloc(HTAB*hashp);
66-
staticboolelement_alloc(HTAB*hashp);
66+
staticboolelement_alloc(HTAB*hashp,intnelem);
6767
staticbooldir_realloc(HTAB*hashp);
6868
staticboolexpand_table(HTAB*hashp);
6969
staticboolhdefault(HTAB*hashp);
@@ -228,11 +228,26 @@ hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
228228
CurrentDynaHashCxt=hashp->hcxt;
229229
}
230230

231+
/* Build the hash directory structure */
231232
if (!init_htab(hashp,nelem))
232233
{
233234
hash_destroy(hashp);
234235
returnNULL;
235236
}
237+
238+
/*
239+
* For a shared hash table, preallocate the requested number of elements.
240+
* This reduces problems with run-time out-of-shared-memory conditions.
241+
*/
242+
if (flags&HASH_SHARED_MEM)
243+
{
244+
if (!element_alloc(hashp, (int)nelem))
245+
{
246+
hash_destroy(hashp);
247+
returnNULL;
248+
}
249+
}
250+
236251
returnhashp;
237252
}
238253

@@ -631,7 +646,7 @@ hash_search(HTAB *hashp,
631646
if (currBucket==NULL)
632647
{
633648
/* no free elements. allocate another chunk of buckets */
634-
if (!element_alloc(hashp))
649+
if (!element_alloc(hashp,HASHELEMENT_ALLOC_INCR))
635650
returnNULL;/* out of memory */
636651
currBucket=hctl->freeList;
637652
Assert(currBucket!=NULL);
@@ -898,7 +913,7 @@ seg_alloc(HTAB *hashp)
898913
* allocate some new elements and link them into the free list
899914
*/
900915
staticbool
901-
element_alloc(HTAB*hashp)
916+
element_alloc(HTAB*hashp,intnelem)
902917
{
903918
HASHHDR*hctl=hashp->hctl;
904919
SizeelementSize;
@@ -910,13 +925,13 @@ element_alloc(HTAB *hashp)
910925

911926
CurrentDynaHashCxt=hashp->hcxt;
912927
tmpElement= (HASHELEMENT*)
913-
hashp->alloc(HASHELEMENT_ALLOC_INCR*elementSize);
928+
hashp->alloc(nelem*elementSize);
914929

915930
if (!tmpElement)
916931
return false;
917932

918933
/* link all the new entries into the freelist */
919-
for (i=0;i<HASHELEMENT_ALLOC_INCR;i++)
934+
for (i=0;i<nelem;i++)
920935
{
921936
tmpElement->link=hctl->freeList;
922937
hctl->freeList=tmpElement;

‎src/include/storage/shmem.h

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/storage/shmem.h,v 1.42 2004/08/29 04:13:10 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/storage/shmem.h,v 1.43 2004/09/28 20:46:35 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -73,8 +73,8 @@ extern void *ShmemInitStruct(const char *name, Size size, bool *foundPtr);
7373
/* size constants for the shmem index table */
7474
/* max size of data structure string name */
7575
#defineSHMEM_INDEX_KEYSIZE (48)
76-
/*maximum size of the shmem index table */
77-
#defineSHMEM_INDEX_SIZE (100)
76+
/*max size of the shmem index table (not a hard limit) */
77+
#defineSHMEM_INDEX_SIZE (32)
7878

7979
/* this is a hash bucket in the shmem index table */
8080
typedefstruct

‎src/include/utils/hsearch.h

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.32 2004/08/29 05:06:59 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.33 2004/09/28 20:46:37 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -135,7 +135,7 @@ typedef struct HASHCTL
135135
#defineHASH_FFACTOR0x008/* Set fill factor */
136136
#defineHASH_FUNCTION0x010/* Set user defined hash function */
137137
#defineHASH_ELEM0x020/* Set key/entry size */
138-
#defineHASH_SHARED_MEM 0x040/*Set shared mem const */
138+
#defineHASH_SHARED_MEM 0x040/*Hashtable is in shared memory */
139139
#defineHASH_ATTACH0x080/* Do not initialize hctl */
140140
#defineHASH_ALLOC0x100/* Set memory allocator */
141141
#defineHASH_CONTEXT0x200/* Set explicit memory context */

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