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Micro-optimizations and comment fixes on the mem5.c memory allocator module.

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FossilOrigin-Name: 8bf5e056eb8beb6e0ed5874fb24d7fe9f0b66d2b
This commit is contained in:
drh
2015-12-18 16:29:47 +00:00
parent 1db0a72be2
commit d319b8c143
3 changed files with 17 additions and 26 deletions
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29
src/mem5.c
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@@ -25,7 +25,7 @@
**
** This memory allocator uses the following algorithm:
**
** 1. All memory allocations sizes are rounded up to a power of 2.
** 1. All memory allocation sizes are rounded up to a power of 2.
**
** 2. If two adjacent free blocks are the halves of a larger block,
** then the two blocks are coalesced into the single larger block.
@@ -117,7 +117,7 @@ static SQLITE_WSD struct Mem5Global {
/*
** Lists of free blocks. aiFreelist[0] is a list of free blocks of
** size mem5.szAtom. aiFreelist[1] holds blocks of size szAtom*2.
** and so forth.
** aiFreelist[2] holds free blocks of size szAtom*4. And so forth.
*/
int aiFreelist[LOGMAX+1];
@@ -183,9 +183,7 @@ static void memsys5Link(int i, int iLogsize){
}
/*
** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
** will already be held (obtained by code in malloc.c) if
** sqlite3GlobalConfig.bMemStat is true.
** Obtain or release the mutex needed to access global data structures.
*/
static void memsys5Enter(void){
sqlite3_mutex_enter(mem5.mutex);
@@ -195,9 +193,8 @@ static void memsys5Leave(void){
}
/*
** Return the size of an outstanding allocation, in bytes. The
** size returned omits the 8-byte header overhead. This only
** works for chunks that are currently checked out.
** Return the size of an outstanding allocation, in bytes.
** This only works for chunks that are currently checked out.
*/
static int memsys5Size(void *p){
int iSize, i;
@@ -230,16 +227,12 @@ static void *memsys5MallocUnsafe(int nByte){
/* Keep track of the maximum allocation request. Even unfulfilled
** requests are counted */
if( (u32)nByte>mem5.maxRequest ){
/* Abort if the requested allocation size is larger than the largest
** power of two that we can represent using 32-bit signed integers. */
if( nByte > 0x40000000 ) return 0;
mem5.maxRequest = nByte;
}
/* Abort if the requested allocation size is larger than the largest
** power of two that we can represent using 32-bit signed integers.
*/
if( nByte > 0x40000000 ){
return 0;
}
/* Round nByte up to the next valid power of two */
for(iFullSz=mem5.szAtom,iLogsize=0; iFullSz<nByte; iFullSz*=2,iLogsize++){}
@@ -398,13 +391,11 @@ static void *memsys5Realloc(void *pPrior, int nBytes){
if( nBytes<=nOld ){
return pPrior;
}
memsys5Enter();
p = memsys5MallocUnsafe(nBytes);
p = memsys5Malloc(nBytes);
if( p ){
memcpy(p, pPrior, nOld);
memsys5FreeUnsafe(pPrior);
memsys5Free(pPrior);
}
memsys5Leave();
return p;
}