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Remove the rarely-used scratch memory allocator. This makes the code smaller,

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faster, and easier to maintain.  In place of the scratch allocator, add the
SQLITE_CONFIG_SMALL_MALLOC configuration option that provides a hint to SQLite
that large memory allocations should be avoided.

FossilOrigin-Name: 54b000246cfb5c7b8adb61a17357ef5a49adddde9e48e8937834d5ba0beb8a6b
This commit is contained in:
drh
2017-08-28 15:51:35 +00:00
parent b3c4523c58
commit b2a0f75c06
19 changed files with 71 additions and 517 deletions
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141
src/malloc.c
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@@ -32,14 +32,6 @@ int sqlite3_release_memory(int n){
#endif
}
/*
** An instance of the following object records the location of
** each unused scratch buffer.
*/
typedef struct ScratchFreeslot {
struct ScratchFreeslot *pNext; /* Next unused scratch buffer */
} ScratchFreeslot;
/*
** State information local to the memory allocation subsystem.
*/
@@ -47,22 +39,12 @@ static SQLITE_WSD struct Mem0Global {
sqlite3_mutex *mutex; /* Mutex to serialize access */
sqlite3_int64 alarmThreshold; /* The soft heap limit */
/*
** Pointers to the end of sqlite3GlobalConfig.pScratch memory
** (so that a range test can be used to determine if an allocation
** being freed came from pScratch) and a pointer to the list of
** unused scratch allocations.
*/
void *pScratchEnd;
ScratchFreeslot *pScratchFree;
u32 nScratchFree;
/*
** True if heap is nearly "full" where "full" is defined by the
** sqlite3_soft_heap_limit() setting.
*/
int nearlyFull;
} mem0 = { 0, 0, 0, 0, 0, 0 };
} mem0 = { 0, 0, 0 };
#define mem0 GLOBAL(struct Mem0Global, mem0)
@@ -132,28 +114,6 @@ int sqlite3MallocInit(void){
}
memset(&mem0, 0, sizeof(mem0));
mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
if( sqlite3GlobalConfig.pScratch && sqlite3GlobalConfig.szScratch>=100
&& sqlite3GlobalConfig.nScratch>0 ){
int i, n, sz;
ScratchFreeslot *pSlot;
sz = ROUNDDOWN8(sqlite3GlobalConfig.szScratch);
sqlite3GlobalConfig.szScratch = sz;
pSlot = (ScratchFreeslot*)sqlite3GlobalConfig.pScratch;
n = sqlite3GlobalConfig.nScratch;
mem0.pScratchFree = pSlot;
mem0.nScratchFree = n;
for(i=0; i<n-1; i++){
pSlot->pNext = (ScratchFreeslot*)(sz+(char*)pSlot);
pSlot = pSlot->pNext;
}
pSlot->pNext = 0;
mem0.pScratchEnd = (void*)&pSlot[1];
}else{
mem0.pScratchEnd = 0;
sqlite3GlobalConfig.pScratch = 0;
sqlite3GlobalConfig.szScratch = 0;
sqlite3GlobalConfig.nScratch = 0;
}
if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
|| sqlite3GlobalConfig.nPage<=0 ){
sqlite3GlobalConfig.pPage = 0;
@@ -304,105 +264,6 @@ void *sqlite3_malloc64(sqlite3_uint64 n){
return sqlite3Malloc(n);
}
/*
** Each thread may only have a single outstanding allocation from
** xScratchMalloc(). We verify this constraint in the single-threaded
** case by setting scratchAllocOut to 1 when an allocation
** is outstanding clearing it when the allocation is freed.
*/
#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
static int scratchAllocOut = 0;
#endif
/*
** Allocate memory that is to be used and released right away.
** This routine is similar to alloca() in that it is not intended
** for situations where the memory might be held long-term. This
** routine is intended to get memory to old large transient data
** structures that would not normally fit on the stack of an
** embedded processor.
*/
void *sqlite3ScratchMalloc(int n){
void *p;
assert( n>0 );
sqlite3_mutex_enter(mem0.mutex);
sqlite3StatusHighwater(SQLITE_STATUS_SCRATCH_SIZE, n);
if( mem0.nScratchFree && sqlite3GlobalConfig.szScratch>=n ){
p = mem0.pScratchFree;
mem0.pScratchFree = mem0.pScratchFree->pNext;
mem0.nScratchFree--;
sqlite3StatusUp(SQLITE_STATUS_SCRATCH_USED, 1);
sqlite3_mutex_leave(mem0.mutex);
}else{
sqlite3_mutex_leave(mem0.mutex);
p = sqlite3Malloc(n);
if( sqlite3GlobalConfig.bMemstat && p ){
sqlite3_mutex_enter(mem0.mutex);
sqlite3StatusUp(SQLITE_STATUS_SCRATCH_OVERFLOW, sqlite3MallocSize(p));
sqlite3_mutex_leave(mem0.mutex);
}
sqlite3MemdebugSetType(p, MEMTYPE_SCRATCH);
}
assert( sqlite3_mutex_notheld(mem0.mutex) );
#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
/* EVIDENCE-OF: R-12970-05880 SQLite will not use more than one scratch
** buffers per thread.
**
** This can only be checked in single-threaded mode.
*/
assert( scratchAllocOut==0 );
if( p ) scratchAllocOut++;
#endif
return p;
}
void sqlite3ScratchFree(void *p){
if( p ){
#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
/* Verify that no more than two scratch allocation per thread
** is outstanding at one time. (This is only checked in the
** single-threaded case since checking in the multi-threaded case
** would be much more complicated.) */
assert( scratchAllocOut>=1 && scratchAllocOut<=2 );
scratchAllocOut--;
#endif
if( SQLITE_WITHIN(p, sqlite3GlobalConfig.pScratch, mem0.pScratchEnd) ){
/* Release memory from the SQLITE_CONFIG_SCRATCH allocation */
ScratchFreeslot *pSlot;
pSlot = (ScratchFreeslot*)p;
sqlite3_mutex_enter(mem0.mutex);
pSlot->pNext = mem0.pScratchFree;
mem0.pScratchFree = pSlot;
mem0.nScratchFree++;
assert( mem0.nScratchFree <= (u32)sqlite3GlobalConfig.nScratch );
sqlite3StatusDown(SQLITE_STATUS_SCRATCH_USED, 1);
sqlite3_mutex_leave(mem0.mutex);
}else{
/* Release memory back to the heap */
assert( sqlite3MemdebugHasType(p, MEMTYPE_SCRATCH) );
assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_SCRATCH) );
sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
if( sqlite3GlobalConfig.bMemstat ){
int iSize = sqlite3MallocSize(p);
sqlite3_mutex_enter(mem0.mutex);
sqlite3StatusDown(SQLITE_STATUS_SCRATCH_OVERFLOW, iSize);
sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, iSize);
sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
sqlite3GlobalConfig.m.xFree(p);
sqlite3_mutex_leave(mem0.mutex);
}else{
sqlite3GlobalConfig.m.xFree(p);
}
}
}
}
/*
** TRUE if p is a lookaside memory allocation from db
*/