Following the code in mem1.c, Why SQLite Use Different Malloc Zone While CPU
Count 1?
static int sqlite3MemInit(void *NotUsed){
#if defined(__APPLE__) !defined(SQLITE_WITHOUT_ZONEMALLOC)
int cpuCount;
size_t len;
if( _sqliteZone_ ){
return SQLITE_OK;
}
len = sizeof(cpuCount);
/* One usually wants to use hw.acctivecpu for MT decisions, but not here */
sysctlbyname("hw.ncpu", cpuCount, len, NULL, 0);
if( cpuCount1 ){
/* defer MT decisions to system malloc */
_sqliteZone_ = malloc_default_zone();
}else{
/* only 1 core, use our own zone to contention over global locks,
** e.g. we have our own dedicated locks */
bool success;
malloc_zone_t* newzone = malloc_create_zone(4096, 0);
malloc_set_zone_name(newzone, "Sqlite_Heap");
do{
success = OSAtomicCompareAndSwapPtrBarrier(NULL, newzone,
(void * volatile *)_sqliteZone_);
}while(!_sqliteZone_);
if( !success ){
/* somebody registered a zone first */
malloc_destroy_zone(newzone);
}
}
#endif
UNUSED_PARAMETER(NotUsed);
return SQLITE_OK;
}
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