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hlinnakahlinnaka
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Avoid allocations in critical sections.
If a palloc in a critical section fails, it becomes a PANIC.
1 parent 447e237 commit 895243d

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3 files changed

+43
-43
lines changed

3 files changed

+43
-43
lines changed

‎src/backend/access/nbtree/nbtinsert.c

Lines changed: 29 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -1840,8 +1840,10 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
18401840
BTPageOpaque rootopaque;
18411841
ItemId itemid;
18421842
IndexTuple item;
1843-
Size itemsz;
1844-
IndexTuple new_item;
1843+
IndexTuple left_item;
1844+
Size left_item_sz;
1845+
IndexTuple right_item;
1846+
Size right_item_sz;
18451847
Buffer metabuf;
18461848
Page metapg;
18471849
BTMetaPageData *metad;
@@ -1860,6 +1862,26 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
18601862
metapg = BufferGetPage(metabuf);
18611863
metad = BTPageGetMeta(metapg);
18621864

1865+
/*
1866+
* Create downlink item for left page (old root). Since this will be the
1867+
* first item in a non-leaf page, it implicitly has minus-infinity key
1868+
* value, so we need not store any actual key in it.
1869+
*/
1870+
left_item_sz = sizeof(IndexTupleData);
1871+
left_item = (IndexTuple) palloc(left_item_sz);
1872+
left_item->t_info = left_item_sz;
1873+
ItemPointerSet(&(left_item->t_tid), lbkno, P_HIKEY);
1874+
1875+
/*
1876+
* Create downlink item for right page. The key for it is obtained from
1877+
* the "high key" position in the left page.
1878+
*/
1879+
itemid = PageGetItemId(lpage, P_HIKEY);
1880+
right_item_sz = ItemIdGetLength(itemid);
1881+
item = (IndexTuple) PageGetItem(lpage, itemid);
1882+
right_item = CopyIndexTuple(item);
1883+
ItemPointerSet(&(right_item->t_tid), rbkno, P_HIKEY);
1884+
18631885
/* NO EREPORT(ERROR) from here till newroot op is logged */
18641886
START_CRIT_SECTION();
18651887

@@ -1877,16 +1899,6 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
18771899
metad->btm_fastroot = rootblknum;
18781900
metad->btm_fastlevel = rootopaque->btpo.level;
18791901

1880-
/*
1881-
* Create downlink item for left page (old root). Since this will be the
1882-
* first item in a non-leaf page, it implicitly has minus-infinity key
1883-
* value, so we need not store any actual key in it.
1884-
*/
1885-
itemsz = sizeof(IndexTupleData);
1886-
new_item = (IndexTuple) palloc(itemsz);
1887-
new_item->t_info = itemsz;
1888-
ItemPointerSet(&(new_item->t_tid), lbkno, P_HIKEY);
1889-
18901902
/*
18911903
* Insert the left page pointer into the new root page. The root page is
18921904
* the rightmost page on its level so there is no "high key" in it; the
@@ -1895,32 +1907,20 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
18951907
* Note: we *must* insert the two items in item-number order, for the
18961908
* benefit of _bt_restore_page().
18971909
*/
1898-
if (PageAddItem(rootpage, (Item) new_item, itemsz, P_HIKEY,
1910+
if (PageAddItem(rootpage, (Item) left_item, left_item_sz, P_HIKEY,
18991911
false, false) == InvalidOffsetNumber)
19001912
elog(PANIC, "failed to add leftkey to new root page"
19011913
" while splitting block %u of index \"%s\"",
19021914
BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
1903-
pfree(new_item);
1904-
1905-
/*
1906-
* Create downlink item for right page. The key for it is obtained from
1907-
* the "high key" position in the left page.
1908-
*/
1909-
itemid = PageGetItemId(lpage, P_HIKEY);
1910-
itemsz = ItemIdGetLength(itemid);
1911-
item = (IndexTuple) PageGetItem(lpage, itemid);
1912-
new_item = CopyIndexTuple(item);
1913-
ItemPointerSet(&(new_item->t_tid), rbkno, P_HIKEY);
19141915

19151916
/*
19161917
* insert the right page pointer into the new root page.
19171918
*/
1918-
if (PageAddItem(rootpage, (Item) new_item, itemsz, P_FIRSTKEY,
1919+
if (PageAddItem(rootpage, (Item) right_item, right_item_sz, P_FIRSTKEY,
19191920
false, false) == InvalidOffsetNumber)
19201921
elog(PANIC, "failed to add rightkey to new root page"
19211922
" while splitting block %u of index \"%s\"",
19221923
BufferGetBlockNumber(lbuf), RelationGetRelationName(rel));
1923-
pfree(new_item);
19241924

19251925
MarkBufferDirty(rootbuf);
19261926
MarkBufferDirty(metabuf);
@@ -1968,6 +1968,9 @@ _bt_newroot(Relation rel, Buffer lbuf, Buffer rbuf)
19681968
/* done with metapage */
19691969
_bt_relbuf(rel, metabuf);
19701970

1971+
pfree(left_item);
1972+
pfree(right_item);
1973+
19711974
return rootbuf;
19721975
}
19731976

‎src/backend/access/transam/xlog.c

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -2348,6 +2348,7 @@ XLogFileInit(uint32 log, uint32 seg,
23482348
{
23492349
char path[MAXPGPATH];
23502350
char tmppath[MAXPGPATH];
2351+
char zbuffer_raw[BLCKSZ + MAXIMUM_ALIGNOF];
23512352
char *zbuffer;
23522353
uint32 installed_log;
23532354
uint32 installed_seg;
@@ -2405,11 +2406,11 @@ XLogFileInit(uint32 log, uint32 seg,
24052406
* fdatasync(2) or O_DSYNC will be sufficient to sync future writes to the
24062407
* log file.
24072408
*
2408-
* Note: palloc zbuffer, instead of just using a local char array, to
2409-
* ensure it is reasonably well-aligned; this may save a few cycles
2410-
* transferring data to the kernel.
2409+
* Note: ensure the buffer is reasonably well-aligned; this may save a few
2410+
* cycles transferring data to the kernel.
24112411
*/
2412-
zbuffer = (char *) palloc0(XLOG_BLCKSZ);
2412+
zbuffer = (char *) MAXALIGN(zbuffer_raw);
2413+
memset(zbuffer, 0, BLCKSZ);
24132414
for (nbytes = 0; nbytes < XLogSegSize; nbytes += XLOG_BLCKSZ)
24142415
{
24152416
errno = 0;
@@ -2429,7 +2430,6 @@ XLogFileInit(uint32 log, uint32 seg,
24292430
errmsg("could not write to file \"%s\": %m", tmppath)));
24302431
}
24312432
}
2432-
pfree(zbuffer);
24332433

24342434
if (pg_fsync(fd) != 0)
24352435
ereport(ERROR,

‎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.h"
18+
#include "access/itup.h"
1819
#include "storage/bufpage.h"
1920

2021

@@ -363,8 +364,6 @@ PageRepairFragmentation(Page page)
363364
Offset pd_lower = ((PageHeader) page)->pd_lower;
364365
Offset pd_upper = ((PageHeader) page)->pd_upper;
365366
Offset pd_special = ((PageHeader) page)->pd_special;
366-
itemIdSort itemidbase,
367-
itemidptr;
368367
ItemId lp;
369368
int nline,
370369
nstorage,
@@ -414,10 +413,11 @@ PageRepairFragmentation(Page page)
414413
((PageHeader) page)->pd_upper = pd_special;
415414
}
416415
else
417-
{ /* nstorage != 0 */
416+
{
418417
/* Need to compact the page the hard way */
419-
itemidbase = (itemIdSort) palloc(sizeof(itemIdSortData) * nstorage);
420-
itemidptr = itemidbase;
418+
itemIdSortData itemidbase[MaxHeapTuplesPerPage];
419+
itemIdSort itemidptr = itemidbase;
420+
421421
totallen = 0;
422422
for (i = 0; i < nline; i++)
423423
{
@@ -462,8 +462,6 @@ PageRepairFragmentation(Page page)
462462
}
463463

464464
((PageHeader) page)->pd_upper = upper;
465-
466-
pfree(itemidbase);
467465
}
468466

469467
/* Set hint bit for PageAddItem */
@@ -712,8 +710,8 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
712710
Offset pd_lower = phdr->pd_lower;
713711
Offset pd_upper = phdr->pd_upper;
714712
Offset pd_special = phdr->pd_special;
715-
itemIdSort itemidbase,
716-
itemidptr;
713+
itemIdSortData itemidbase[MaxIndexTuplesPerPage];
714+
itemIdSort itemidptr;
717715
ItemId lp;
718716
int nline,
719717
nused;
@@ -725,6 +723,8 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
725723
int nextitm;
726724
OffsetNumber offnum;
727725

726+
Assert(nitems < MaxIndexTuplesPerPage);
727+
728728
/*
729729
* If there aren't very many items to delete, then retail
730730
* PageIndexTupleDelete is the best way. Delete the items in reverse
@@ -759,7 +759,6 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
759759
* still validity-checking.
760760
*/
761761
nline = PageGetMaxOffsetNumber(page);
762-
itemidbase = (itemIdSort) palloc(sizeof(itemIdSortData) * nline);
763762
itemidptr = itemidbase;
764763
totallen = 0;
765764
nused = 0;
@@ -825,6 +824,4 @@ PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
825824

826825
phdr->pd_lower = SizeOfPageHeaderData + nused * sizeof(ItemIdData);
827826
phdr->pd_upper = upper;
828-
829-
pfree(itemidbase);
830827
}

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