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Commit16be2fd

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Make dsa_allocate interface more like MemoryContextAlloc.
A new function dsa_allocate_extended now takes flags which indicatethat huge allocations should be permitted, that out-of-memoryconditions should not throw an error, and/or that the returned memoryshould be zero-filled, just like MemoryContextAllocateExtended.Commit9acb855, which addeddsa_allocate0, was broken because it failed to account for thepossibility that dsa_allocate() might return InvalidDsaPointer.This fixes that problem along the way.Thomas Munro, with some comment changes by me.Discussion:http://postgr.es/m/CA+Tgmobt7CcF_uQP2UQwWmu4K9qCHehMJP9_9m1urwP8hbOeHQ@mail.gmail.com
1 parent1a16af8 commit16be2fd

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2 files changed

+69
-23
lines changed

2 files changed

+69
-23
lines changed

‎src/backend/utils/mmgr/dsa.c‎

Lines changed: 55 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -642,18 +642,39 @@ dsa_pin_mapping(dsa_area *area)
642642
/*
643643
* Allocate memory in this storage area. The return value is a dsa_pointer
644644
* that can be passed to other processes, and converted to a local pointer
645-
* with dsa_get_address. If no memory is available, returns
646-
* InvalidDsaPointer.
645+
* with dsa_get_address. 'flags' is a bitmap which should be constructed
646+
* from the following values:
647+
*
648+
* DSA_ALLOC_HUGE allows allocations >= 1GB. Otherwise, such allocations
649+
* will result in an ERROR.
650+
*
651+
* DSA_ALLOC_NO_OOM causes this function to return InvalidDsaPointer when
652+
* no memory is available or a size limit establed by set_dsa_size_limit
653+
* would be exceeded. Otherwise, such allocations will result in an ERROR.
654+
*
655+
* DSA_ALLOC_ZERO causes the allocated memory to be zeroed. Otherwise, the
656+
* contents of newly-allocated memory are indeterminate.
657+
*
658+
* These flags correspond to similarly named flags used by
659+
* MemoryContextAllocExtended(). See also the macros dsa_allocate and
660+
* dsa_allocate0 which expand to a call to this function with commonly used
661+
* flags.
647662
*/
648663
dsa_pointer
649-
dsa_allocate(dsa_area*area,Sizesize)
664+
dsa_allocate_extended(dsa_area*area,Sizesize,intflags)
650665
{
651666
uint16size_class;
652667
dsa_pointerstart_pointer;
653668
dsa_segment_map*segment_map;
669+
dsa_pointerresult;
654670

655671
Assert(size>0);
656672

673+
/* Sanity check on huge individual allocation size. */
674+
if (((flags&DSA_ALLOC_HUGE)!=0&& !AllocHugeSizeIsValid(size))||
675+
((flags&DSA_ALLOC_HUGE)==0&& !AllocSizeIsValid(size)))
676+
elog(ERROR,"invalid DSA memory alloc request size %zu",size);
677+
657678
/*
658679
* If bigger than the largest size class, just grab a run of pages from
659680
* the free page manager, instead of allocating an object from a pool.
@@ -684,6 +705,14 @@ dsa_allocate(dsa_area *area, Size size)
684705
/* Can't make any more segments: game over. */
685706
LWLockRelease(DSA_AREA_LOCK(area));
686707
dsa_free(area,span_pointer);
708+
709+
/* Raise error unless asked not to. */
710+
if ((flags&MCXT_ALLOC_NO_OOM)==0)
711+
ereport(ERROR,
712+
(errcode(ERRCODE_OUT_OF_MEMORY),
713+
errmsg("out of memory"),
714+
errdetail("Failed on DSA request of size %zu.",
715+
size)));
687716
returnInvalidDsaPointer;
688717
}
689718

@@ -710,6 +739,10 @@ dsa_allocate(dsa_area *area, Size size)
710739
segment_map->pagemap[first_page]=span_pointer;
711740
LWLockRelease(DSA_SCLASS_LOCK(area,DSA_SCLASS_SPAN_LARGE));
712741

742+
/* Zero-initialize the memory if requested. */
743+
if ((flags&DSA_ALLOC_ZERO)!=0)
744+
memset(dsa_get_address(area,start_pointer),0,size);
745+
713746
returnstart_pointer;
714747
}
715748

@@ -748,27 +781,28 @@ dsa_allocate(dsa_area *area, Size size)
748781
Assert(size <=dsa_size_classes[size_class]);
749782
Assert(size_class==0||size>dsa_size_classes[size_class-1]);
750783

751-
/*
752-
* Attempt to allocate an object from the appropriate pool. This might
753-
* return InvalidDsaPointer if there's no space available.
754-
*/
755-
returnalloc_object(area,size_class);
756-
}
784+
/* Attempt to allocate an object from the appropriate pool. */
785+
result=alloc_object(area,size_class);
757786

758-
/*
759-
* As dsa_allocate, but zeroes the allocated memory.
760-
*/
761-
dsa_pointer
762-
dsa_allocate0(dsa_area*area,Sizesize)
763-
{
764-
dsa_pointerdp;
765-
char*object;
787+
/* Check for failure to allocate. */
788+
if (!DsaPointerIsValid(result))
789+
{
790+
/* Raise error unless asked not to. */
791+
if ((flags&DSA_ALLOC_NO_OOM)==0)
792+
{
793+
ereport(ERROR,
794+
(errcode(ERRCODE_OUT_OF_MEMORY),
795+
errmsg("out of memory"),
796+
errdetail("Failed on DSA request of size %zu.",size)));
797+
}
798+
returnInvalidDsaPointer;
799+
}
766800

767-
dp=dsa_allocate(area,size);
768-
object=dsa_get_address(area,dp);
769-
memset(object,0,size);
801+
/* Zero-initialize the memory if requested. */
802+
if ((flags&DSA_ALLOC_ZERO)!=0)
803+
memset(dsa_get_address(area,result),0,size);
770804

771-
returndp;
805+
returnresult;
772806
}
773807

774808
/*

‎src/include/utils/dsa.h‎

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -71,12 +71,25 @@ typedef pg_atomic_uint64 dsa_pointer_atomic;
7171
#defineDSA_POINTER_FORMAT "%016" INT64_MODIFIER "x"
7272
#endif
7373

74+
/* Flags for dsa_allocate_extended. */
75+
#defineDSA_ALLOC_HUGE0x01/* allow huge allocation (> 1 GB) */
76+
#defineDSA_ALLOC_NO_OOM0x02/* no failure if out-of-memory */
77+
#defineDSA_ALLOC_ZERO0x04/* zero allocated memory */
78+
7479
/* A sentinel value for dsa_pointer used to indicate failure to allocate. */
7580
#defineInvalidDsaPointer ((dsa_pointer) 0)
7681

7782
/* Check if a dsa_pointer value is valid. */
7883
#defineDsaPointerIsValid(x) ((x) != InvalidDsaPointer)
7984

85+
/* Allocate uninitialized memory with error on out-of-memory. */
86+
#definedsa_allocate(area,size) \
87+
dsa_allocate_extended(area, size, 0)
88+
89+
/* Allocate zero-initialized memory with error on out-of-memory. */
90+
#definedsa_allocate0(area,size) \
91+
dsa_allocate_extended(area, size, DSA_ALLOC_ZERO)
92+
8093
/*
8194
* The type used for dsa_area handles. dsa_handle values can be shared with
8295
* other processes, so that they can attach to them. This provides a way to
@@ -105,8 +118,7 @@ extern void dsa_unpin(dsa_area *area);
105118
externvoiddsa_set_size_limit(dsa_area*area,Sizelimit);
106119
externSizedsa_minimum_size(void);
107120
externdsa_handledsa_get_handle(dsa_area*area);
108-
externdsa_pointerdsa_allocate(dsa_area*area,Sizesize);
109-
externdsa_pointerdsa_allocate0(dsa_area*area,Sizesize);
121+
externdsa_pointerdsa_allocate_extended(dsa_area*area,Sizesize,intflags);
110122
externvoiddsa_free(dsa_area*area,dsa_pointerdp);
111123
externvoid*dsa_get_address(dsa_area*area,dsa_pointerdp);
112124
externvoiddsa_trim(dsa_area*area);

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