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Commit3788c66

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Improve various places that double the size of a buffer
Several places were performing a tight loop to determine the first powerof 2 number that's > or >= the required memory. Instead of using a loopfor that, we can use pg_nextpower2_32 or pg_nextpower2_64. When we need apower of 2 number equal to or greater than a given amount, we just passthe amount to the nextpower2 function. When we need a power of 2 greaterthan the amount, we just pass the amount + 1.Additionally, in tsearch there were a couple of locations that wereperforming a while loop when a simple "if" would have done. In both ofthese locations only 1 item is being added, so the loop could only haveever iterated once. Changing the loop into an if statement makes the codevery slightly more optimal as the condition is checked once rather thantwice.There are quite a few remaining locations that increase the size of thebuffer in the following form: while (reqsize >= buflen) { buflen *= 2; buf = repalloc(buf, buflen); }These are not touched in this commit. repalloc will error out for sizeslarger than MaxAllocSize. Changing these to use pg_nextpower2_32 wouldremove the chance of that error being raised. It's unclear from the codeif the sizes could ever become that large, so err on the side of caution.Discussion:https://postgr.es/m/CAApHDvp=tns7RL4PH0ZR0M+M-YFLquK7218x=0B_zO+DbOma+w@mail.gmail.comReviewed-by: Zhihong Yu
1 parente45b0df commit3788c66

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7 files changed

+21
-24
lines changed

7 files changed

+21
-24
lines changed

‎src/backend/parser/scan.l

Lines changed: 2 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -39,6 +39,7 @@
3939
#include "parser/gramparse.h"
4040
#include "parser/parser.h"/* only needed for GUC variables */
4141
#include "parser/scansup.h"
42+
#include "port/pg_bitutils.h"
4243
#include "mb/pg_wchar.h"
4344
}
4445

@@ -1253,10 +1254,7 @@ addlit(char *ytext, int yleng, core_yyscan_t yyscanner)
12531254
/* enlarge buffer if needed */
12541255
if ((yyextra->literallen + yleng) >= yyextra->literalalloc)
12551256
{
1256-
do
1257-
{
1258-
yyextra->literalalloc *=2;
1259-
}while ((yyextra->literallen + yleng) >= yyextra->literalalloc);
1257+
yyextra->literalalloc =pg_nextpower2_32(yyextra->literallen + yleng +1);
12601258
yyextra->literalbuf = (char *)repalloc(yyextra->literalbuf,
12611259
yyextra->literalalloc);
12621260
}

‎src/backend/storage/ipc/shm_mq.c

Lines changed: 9 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -20,6 +20,7 @@
2020

2121
#include"miscadmin.h"
2222
#include"pgstat.h"
23+
#include"port/pg_bitutils.h"
2324
#include"postmaster/bgworker.h"
2425
#include"storage/procsignal.h"
2526
#include"storage/shm_mq.h"
@@ -720,14 +721,17 @@ shm_mq_receive(shm_mq_handle *mqh, Size *nbytesp, void **datap, bool nowait)
720721
*/
721722
if (mqh->mqh_buflen<nbytes)
722723
{
723-
Sizenewbuflen=Max(mqh->mqh_buflen,MQH_INITIAL_BUFSIZE);
724+
Sizenewbuflen;
724725

725726
/*
726-
*Doublethebuffer size until the payload fits, but limit to
727-
* MaxAllocSize.
727+
*Increase size tothenext power of 2 that's >= nbytes, but
728+
*limit toMaxAllocSize.
728729
*/
729-
while (newbuflen<nbytes)
730-
newbuflen *=2;
730+
#ifSIZEOF_SIZE_T==4
731+
newbuflen=pg_nextpower2_32(nbytes);
732+
#else
733+
newbuflen=pg_nextpower2_64(nbytes);
734+
#endif
731735
newbuflen=Min(newbuflen,MaxAllocSize);
732736

733737
if (mqh->mqh_buffer!=NULL)

‎src/backend/storage/lmgr/lwlock.c

Lines changed: 3 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -79,6 +79,7 @@
7979
#include"miscadmin.h"
8080
#include"pg_trace.h"
8181
#include"pgstat.h"
82+
#include"port/pg_bitutils.h"
8283
#include"postmaster/postmaster.h"
8384
#include"replication/slot.h"
8485
#include"storage/ipc.h"
@@ -659,9 +660,7 @@ LWLockRegisterTranche(int tranche_id, const char *tranche_name)
659660
{
660661
intnewalloc;
661662

662-
newalloc=Max(LWLockTrancheNamesAllocated,8);
663-
while (newalloc <=tranche_id)
664-
newalloc *=2;
663+
newalloc=pg_nextpower2_32(Max(8,tranche_id+1));
665664

666665
if (LWLockTrancheNames==NULL)
667666
LWLockTrancheNames= (constchar**)
@@ -715,10 +714,7 @@ RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)
715714

716715
if (NamedLWLockTrancheRequests >=NamedLWLockTrancheRequestsAllocated)
717716
{
718-
inti=NamedLWLockTrancheRequestsAllocated;
719-
720-
while (i <=NamedLWLockTrancheRequests)
721-
i *=2;
717+
inti=pg_nextpower2_32(NamedLWLockTrancheRequests+1);
722718

723719
NamedLWLockTrancheRequestArray= (NamedLWLockTrancheRequest*)
724720
repalloc(NamedLWLockTrancheRequestArray,

‎src/backend/tsearch/spell.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1600,7 +1600,8 @@ MergeAffix(IspellDict *Conf, int a1, int a2)
16001600
elseif (*Conf->AffixData[a2]=='\0')
16011601
returna1;
16021602

1603-
while (Conf->nAffixData+1 >=Conf->lenAffixData)
1603+
/* Double the size of AffixData if there's not enough space */
1604+
if (Conf->nAffixData+1 >=Conf->lenAffixData)
16041605
{
16051606
Conf->lenAffixData *=2;
16061607
Conf->AffixData= (char**)repalloc(Conf->AffixData,

‎src/backend/tsearch/ts_parse.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -436,7 +436,7 @@ parsetext(Oid cfgId, ParsedText *prs, char *buf, int buflen)
436436
staticvoid
437437
hladdword(HeadlineParsedText*prs,char*buf,intbuflen,inttype)
438438
{
439-
while (prs->curwords >=prs->lenwords)
439+
if (prs->curwords >=prs->lenwords)
440440
{
441441
prs->lenwords *=2;
442442
prs->words= (HeadlineWordEntry*)repalloc((void*)prs->words,prs->lenwords*sizeof(HeadlineWordEntry));

‎src/backend/utils/cache/inval.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -106,6 +106,7 @@
106106
#include"catalog/catalog.h"
107107
#include"catalog/pg_constraint.h"
108108
#include"miscadmin.h"
109+
#include"port/pg_bitutils.h"
109110
#include"storage/sinval.h"
110111
#include"storage/smgr.h"
111112
#include"utils/catcache.h"
@@ -799,8 +800,7 @@ MakeSharedInvalidMessagesArray(const SharedInvalidationMessage *msgs, int n)
799800

800801
if ((numSharedInvalidMessagesArray+n)>maxSharedInvalidMessagesArray)
801802
{
802-
while ((numSharedInvalidMessagesArray+n)>maxSharedInvalidMessagesArray)
803-
maxSharedInvalidMessagesArray *=2;
803+
maxSharedInvalidMessagesArray=pg_nextpower2_32(numSharedInvalidMessagesArray+n);
804804

805805
SharedInvalidMessagesArray=repalloc(SharedInvalidMessagesArray,
806806
maxSharedInvalidMessagesArray

‎src/backend/utils/cache/typcache.c

Lines changed: 2 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -60,6 +60,7 @@
6060
#include"executor/executor.h"
6161
#include"lib/dshash.h"
6262
#include"optimizer/optimizer.h"
63+
#include"port/pg_bitutils.h"
6364
#include"storage/lwlock.h"
6465
#include"utils/builtins.h"
6566
#include"utils/catcache.h"
@@ -1708,10 +1709,7 @@ ensure_record_cache_typmod_slot_exists(int32 typmod)
17081709

17091710
if (typmod >=RecordCacheArrayLen)
17101711
{
1711-
int32newlen=RecordCacheArrayLen*2;
1712-
1713-
while (typmod >=newlen)
1714-
newlen *=2;
1712+
int32newlen=pg_nextpower2_32(typmod+1);
17151713

17161714
RecordCacheArray= (TupleDesc*)repalloc(RecordCacheArray,
17171715
newlen*sizeof(TupleDesc));

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