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Commit1891a4b

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committed
Avoid allocations in critical sections.
If a palloc in a critical section fails, it becomes a PANIC.
1 parentd359f71 commit1891a4b

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4 files changed

+49
-57
lines changed

4 files changed

+49
-57
lines changed

‎src/backend/access/nbtree/nbtinsert.c‎

Lines changed: 29 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -1845,8 +1845,10 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
18451845
BTPageOpaquerootopaque;
18461846
ItemIditemid;
18471847
IndexTupleitem;
1848-
Sizeitemsz;
1849-
IndexTuplenew_item;
1848+
IndexTupleleft_item;
1849+
Sizeleft_item_sz;
1850+
IndexTupleright_item;
1851+
Sizeright_item_sz;
18501852
Buffermetabuf;
18511853
Pagemetapg;
18521854
BTMetaPageData*metad;
@@ -1865,6 +1867,26 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
18651867
metapg=BufferGetPage(metabuf);
18661868
metad=BTPageGetMeta(metapg);
18671869

1870+
/*
1871+
* Create downlink item for left page (old root). Since this will be the
1872+
* first item in a non-leaf page, it implicitly has minus-infinity key
1873+
* value, so we need not store any actual key in it.
1874+
*/
1875+
left_item_sz=sizeof(IndexTupleData);
1876+
left_item= (IndexTuple)palloc(left_item_sz);
1877+
left_item->t_info=left_item_sz;
1878+
ItemPointerSet(&(left_item->t_tid),lbkno,P_HIKEY);
1879+
1880+
/*
1881+
* Create downlink item for right page. The key for it is obtained from
1882+
* the "high key" position in the left page.
1883+
*/
1884+
itemid=PageGetItemId(lpage,P_HIKEY);
1885+
right_item_sz=ItemIdGetLength(itemid);
1886+
item= (IndexTuple)PageGetItem(lpage,itemid);
1887+
right_item=CopyIndexTuple(item);
1888+
ItemPointerSet(&(right_item->t_tid),rbkno,P_HIKEY);
1889+
18681890
/* NO EREPORT(ERROR) from here till newroot op is logged */
18691891
START_CRIT_SECTION();
18701892

@@ -1882,16 +1904,6 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
18821904
metad->btm_fastroot=rootblknum;
18831905
metad->btm_fastlevel=rootopaque->btpo.level;
18841906

1885-
/*
1886-
* Create downlink item for left page (old root). Since this will be the
1887-
* first item in a non-leaf page, it implicitly has minus-infinity key
1888-
* value, so we need not store any actual key in it.
1889-
*/
1890-
itemsz=sizeof(IndexTupleData);
1891-
new_item= (IndexTuple)palloc(itemsz);
1892-
new_item->t_info=itemsz;
1893-
ItemPointerSet(&(new_item->t_tid),lbkno,P_HIKEY);
1894-
18951907
/*
18961908
* Insert the left page pointer into the new root page. The root page is
18971909
* the rightmost page on its level so there is no "high key" in it; the
@@ -1900,32 +1912,20 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
19001912
* Note: we *must* insert the two items in item-number order, for the
19011913
* benefit of _bt_restore_page().
19021914
*/
1903-
if (PageAddItem(rootpage, (Item)new_item,itemsz,P_HIKEY,
1915+
if (PageAddItem(rootpage, (Item)left_item,left_item_sz,P_HIKEY,
19041916
false, false)==InvalidOffsetNumber)
19051917
elog(PANIC,"failed to add leftkey to new root page"
19061918
" while splitting block %u of index \"%s\"",
19071919
BufferGetBlockNumber(lbuf),RelationGetRelationName(rel));
1908-
pfree(new_item);
1909-
1910-
/*
1911-
* Create downlink item for right page. The key for it is obtained from
1912-
* the "high key" position in the left page.
1913-
*/
1914-
itemid=PageGetItemId(lpage,P_HIKEY);
1915-
itemsz=ItemIdGetLength(itemid);
1916-
item= (IndexTuple)PageGetItem(lpage,itemid);
1917-
new_item=CopyIndexTuple(item);
1918-
ItemPointerSet(&(new_item->t_tid),rbkno,P_HIKEY);
19191920

19201921
/*
19211922
* insert the right page pointer into the new root page.
19221923
*/
1923-
if (PageAddItem(rootpage, (Item)new_item,itemsz,P_FIRSTKEY,
1924+
if (PageAddItem(rootpage, (Item)right_item,right_item_sz,P_FIRSTKEY,
19241925
false, false)==InvalidOffsetNumber)
19251926
elog(PANIC,"failed to add rightkey to new root page"
19261927
" while splitting block %u of index \"%s\"",
19271928
BufferGetBlockNumber(lbuf),RelationGetRelationName(rel));
1928-
pfree(new_item);
19291929

19301930
MarkBufferDirty(rootbuf);
19311931
MarkBufferDirty(metabuf);
@@ -1971,6 +1971,9 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
19711971
/* done with metapage */
19721972
_bt_relbuf(rel,metabuf);
19731973

1974+
pfree(left_item);
1975+
pfree(right_item);
1976+
19741977
returnrootbuf;
19751978
}
19761979

‎src/backend/access/spgist/spgdoinsert.c‎

Lines changed: 3 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -122,7 +122,8 @@ cmpOffsetNumbers(const void *a, const void *b)
122122
*
123123
* NB: this is used during WAL replay, so beware of trying to make it too
124124
* smart. In particular, it shouldn't use "state" except for calling
125-
* spgFormDeadTuple().
125+
* spgFormDeadTuple(). This is also used in a critical section, so no
126+
* pallocs either!
126127
*/
127128
void
128129
spgPageIndexMultiDelete(SpGistState*state,Pagepage,
@@ -131,7 +132,7 @@ spgPageIndexMultiDelete(SpGistState *state, Page page,
131132
BlockNumberblkno,OffsetNumberoffnum)
132133
{
133134
OffsetNumberfirstItem;
134-
OffsetNumber*sortednos;
135+
OffsetNumbersortednos[MaxIndexTuplesPerPage];
135136
SpGistDeadTupletuple=NULL;
136137
inti;
137138

@@ -145,7 +146,6 @@ spgPageIndexMultiDelete(SpGistState *state, Page page,
145146
* replacement tuples.) However, we must not scribble on the caller's
146147
* array, so we have to make a copy.
147148
*/
148-
sortednos= (OffsetNumber*)palloc(sizeof(OffsetNumber)*nitems);
149149
memcpy(sortednos,itemnos,sizeof(OffsetNumber)*nitems);
150150
if (nitems>1)
151151
qsort(sortednos,nitems,sizeof(OffsetNumber),cmpOffsetNumbers);
@@ -173,8 +173,6 @@ spgPageIndexMultiDelete(SpGistState *state, Page page,
173173
elseif (tupstate==SPGIST_PLACEHOLDER)
174174
SpGistPageGetOpaque(page)->nPlaceholder++;
175175
}
176-
177-
pfree(sortednos);
178176
}
179177

180178
/*

‎src/backend/access/transam/xlog.c‎

Lines changed: 8 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -739,9 +739,8 @@ XLogInsert(RmgrId rmid, uint8 info, XLogRecData *rdata)
739739

740740
if (rechdr==NULL)
741741
{
742-
rechdr=malloc(SizeOfXLogRecord);
743-
if (rechdr==NULL)
744-
elog(ERROR,"out of memory");
742+
staticcharrechdrbuf[SizeOfXLogRecord+MAXIMUM_ALIGNOF];
743+
rechdr= (XLogRecord*)MAXALIGN(&rechdrbuf);
745744
MemSet(rechdr,0,SizeOfXLogRecord);
746745
}
747746

@@ -2248,6 +2247,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
22482247
{
22492248
charpath[MAXPGPATH];
22502249
chartmppath[MAXPGPATH];
2250+
charzbuffer_raw[BLCKSZ+MAXIMUM_ALIGNOF];
22512251
char*zbuffer;
22522252
XLogSegNoinstalled_segno;
22532253
intmax_advance;
@@ -2286,16 +2286,6 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
22862286

22872287
unlink(tmppath);
22882288

2289-
/*
2290-
* Allocate a buffer full of zeros. This is done before opening the file
2291-
* so that we don't leak the file descriptor if palloc fails.
2292-
*
2293-
* Note: palloc zbuffer, instead of just using a local char array, to
2294-
* ensure it is reasonably well-aligned; this may save a few cycles
2295-
* transferring data to the kernel.
2296-
*/
2297-
zbuffer= (char*)palloc0(XLOG_BLCKSZ);
2298-
22992289
/* do not use get_sync_bit() here --- want to fsync only at end of fill */
23002290
fd=BasicOpenFile(tmppath,O_RDWR |O_CREAT |O_EXCL |PG_BINARY,
23012291
S_IRUSR |S_IWUSR);
@@ -2312,7 +2302,12 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
23122302
* fsync below) that all the indirect blocks are down on disk.Therefore,
23132303
* fdatasync(2) or O_DSYNC will be sufficient to sync future writes to the
23142304
* log file.
2305+
*
2306+
* Note: ensure the buffer is reasonably well-aligned; this may save a few
2307+
* cycles transferring data to the kernel.
23152308
*/
2309+
zbuffer= (char*)MAXALIGN(zbuffer_raw);
2310+
memset(zbuffer,0,BLCKSZ);
23162311
for (nbytes=0;nbytes<XLogSegSize;nbytes+=XLOG_BLCKSZ)
23172312
{
23182313
errno=0;
@@ -2335,7 +2330,6 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
23352330
errmsg("could not write to file \"%s\": %m",tmppath)));
23362331
}
23372332
}
2338-
pfree(zbuffer);
23392333

23402334
if (pg_fsync(fd)!=0)
23412335
{

‎src/backend/storage/page/bufpage.c‎

Lines changed: 9 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -15,6 +15,7 @@
1515
#include"postgres.h"
1616

1717
#include"access/htup_details.h"
18+
#include"access/itup.h"
1819
#include"access/xlog.h"
1920
#include"storage/checksum.h"
2021
#include"utils/memutils.h"
@@ -418,8 +419,6 @@ PageRepairFragmentation(Page page)
418419
Offsetpd_lower= ((PageHeader)page)->pd_lower;
419420
Offsetpd_upper= ((PageHeader)page)->pd_upper;
420421
Offsetpd_special= ((PageHeader)page)->pd_special;
421-
itemIdSortitemidbase,
422-
itemidptr;
423422
ItemIdlp;
424423
intnline,
425424
nstorage,
@@ -469,10 +468,11 @@ PageRepairFragmentation(Page page)
469468
((PageHeader)page)->pd_upper=pd_special;
470469
}
471470
else
472-
{/* nstorage != 0 */
471+
{
473472
/* Need to compact the page the hard way */
474-
itemidbase= (itemIdSort)palloc(sizeof(itemIdSortData)*nstorage);
475-
itemidptr=itemidbase;
473+
itemIdSortDataitemidbase[MaxHeapTuplesPerPage];
474+
itemIdSortitemidptr=itemidbase;
475+
476476
totallen=0;
477477
for (i=0;i<nline;i++)
478478
{
@@ -517,8 +517,6 @@ PageRepairFragmentation(Page page)
517517
}
518518

519519
((PageHeader)page)->pd_upper=upper;
520-
521-
pfree(itemidbase);
522520
}
523521

524522
/* Set hint bit for PageAddItem */
@@ -767,8 +765,8 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
767765
Offsetpd_lower=phdr->pd_lower;
768766
Offsetpd_upper=phdr->pd_upper;
769767
Offsetpd_special=phdr->pd_special;
770-
itemIdSortitemidbase,
771-
itemidptr;
768+
itemIdSortDataitemidbase[MaxIndexTuplesPerPage];
769+
itemIdSortitemidptr;
772770
ItemIdlp;
773771
intnline,
774772
nused;
@@ -780,6 +778,8 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
780778
intnextitm;
781779
OffsetNumberoffnum;
782780

781+
Assert(nitems<MaxIndexTuplesPerPage);
782+
783783
/*
784784
* If there aren't very many items to delete, then retail
785785
* PageIndexTupleDelete is the best way. Delete the items in reverse
@@ -814,7 +814,6 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
814814
* still validity-checking.
815815
*/
816816
nline=PageGetMaxOffsetNumber(page);
817-
itemidbase= (itemIdSort)palloc(sizeof(itemIdSortData)*nline);
818817
itemidptr=itemidbase;
819818
totallen=0;
820819
nused=0;
@@ -880,8 +879,6 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
880879

881880
phdr->pd_lower=SizeOfPageHeaderData+nused*sizeof(ItemIdData);
882881
phdr->pd_upper=upper;
883-
884-
pfree(itemidbase);
885882
}
886883

887884

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