We can increase the efficiency with the following code replace:
static int memsys5Roundup(int n){//changed by wjf
if( n > 0x40000000 ) return 0;
int i = 0;
while (_BlockSize[i++]<n);
return _BlockSize[i-1];
}
//static int memsys5Roundup(int n){
// int iFullSz;
// if( n > 0x40000000 ) return 0;
// for(iFullSz=mem5.szAtom; iFullSz<n; iFullSz *= 2);
// return iFullSz;
//}
/*
** Initialize the memory allocator.
**
** This routine is not threadsafe. The caller must be holding a mutex
** to prevent multiple threads from entering at the same time.
*/
static int _BlockSize[32];//add by wjf
static int memsys5Init(void *NotUsed){
int ii; /* Loop counter */
int nByte; /* Number of bytes of memory available to this allocator */
u8 *zByte; /* Memory usable by this allocator */
int nMinLog; /* Log base 2 of minimum allocation size in bytes */
int iOffset; /* An offset into mem5.aCtrl[] */
UNUSED_PARAMETER(NotUsed);
/* For the purposes of this routine, disable the mutex */
mem5.mutex = 0;
/* The size of a Mem5Link object must be a power of two. Verify that
** this is case.
*/
assert( (sizeof(Mem5Link)&(sizeof(Mem5Link)-1))==0 );
nByte = sqlite3GlobalConfig.nHeap;
zByte = (u8*)sqlite3GlobalConfig.pHeap;
assert( zByte!=0 ); /* sqlite3_config() does not allow otherwise */
/* boundaries on sqlite3GlobalConfig.mnReq are enforced in sqlite3_config() */
nMinLog = memsys5Log(sqlite3GlobalConfig.mnReq);
mem5.szAtom = (1<<nMinLog);
while( (int)sizeof(Mem5Link)>mem5.szAtom ){
mem5.szAtom = mem5.szAtom << 1;
}
//add by wjf
long long size = mem5.szAtom;
int i = 0;
while (size < 0x40000000) {
_BlockSize[i++] = (int)size;
size *= 2;
}
mem5.nBlock = (nByte / (mem5.szAtom+sizeof(u8)));
mem5.zPool = zByte;
mem5.aCtrl = (u8 *)&mem5.zPool[mem5.nBlock*mem5.szAtom];
for(ii=0; ii<=LOGMAX; ii++){
mem5.aiFreelist[ii] = -1;
}
iOffset = 0;
for(ii=LOGMAX; ii>=0; ii--){
int nAlloc = (1<<ii);
if( (iOffset+nAlloc)<=mem5.nBlock ){
mem5.aCtrl[iOffset] = ii | CTRL_FREE;
memsys5Link(iOffset, ii);
iOffset += nAlloc;
}
assert((iOffset+nAlloc)>mem5.nBlock);
}
/* If a mutex is required for normal operation, allocate one */
if( sqlite3GlobalConfig.bMemstat==0 ){
mem5.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
}
return SQLITE_OK;
}
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