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Remove unnecessary code from malloc.c. Enhance pcache1.c so that is tries

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to reuse existing pages, rather than create new pages, when SQLite is under
memory pressure.  "Memory pressure" means that SQLITE_CONFIG_PAGECACHE memory
is nearly exhausted or sqlite3_soft_heap_limit() has been reached.

FossilOrigin-Name: 51049479a8577e03cc353f71f6e13a10c8323d91
This commit is contained in:
drh
2010-08-27 12:21:06 +00:00
parent 48d9e01e36
commit 50d1b5f363
7 changed files with 109 additions and 54 deletions
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40
src/malloc.c
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@@ -97,7 +97,12 @@ static SQLITE_WSD struct Mem0Global {
** which pages are available.
*/
u32 *aScratchFree;
u32 *aPageFree;
/*
** 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, 0, 0 };
#define mem0 GLOBAL(struct Mem0Global, mem0)
@@ -125,25 +130,24 @@ int sqlite3MallocInit(void){
sqlite3GlobalConfig.pScratch = 0;
sqlite3GlobalConfig.szScratch = 0;
}
if( sqlite3GlobalConfig.pPage && sqlite3GlobalConfig.szPage>=512
&& sqlite3GlobalConfig.nPage>=1 ){
int i;
int overhead;
int sz = ROUNDDOWN8(sqlite3GlobalConfig.szPage);
int n = sqlite3GlobalConfig.nPage;
overhead = (4*n + sz - 1)/sz;
sqlite3GlobalConfig.nPage -= overhead;
mem0.aPageFree = (u32*)&((char*)sqlite3GlobalConfig.pPage)
[sqlite3GlobalConfig.szPage*sqlite3GlobalConfig.nPage];
for(i=0; i<sqlite3GlobalConfig.nPage; i++){ mem0.aPageFree[i] = i; }
mem0.nPageFree = sqlite3GlobalConfig.nPage;
}else{
if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
|| sqlite3GlobalConfig.nPage<1 ){
sqlite3GlobalConfig.pPage = 0;
sqlite3GlobalConfig.szPage = 0;
sqlite3GlobalConfig.nPage = 0;
}
return sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
}
/*
** Return true if the heap is currently under memory pressure - in other
** words if the amount of heap used is close to the limit set by
** sqlite3_soft_heap_limit().
*/
int sqlite3HeapNearlyFull(void){
return mem0.nearlyFull;
}
/*
** Deinitialize the memory allocation subsystem.
*/
@@ -186,10 +190,13 @@ int sqlite3MemoryAlarm(
void *pArg,
sqlite3_int64 iThreshold
){
int nUsed;
sqlite3_mutex_enter(mem0.mutex);
mem0.alarmCallback = xCallback;
mem0.alarmArg = pArg;
mem0.alarmThreshold = iThreshold;
nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
mem0.nearlyFull = (iThreshold>0 && iThreshold<=nUsed);
sqlite3_mutex_leave(mem0.mutex);
return SQLITE_OK;
}
@@ -240,14 +247,19 @@ static int mallocWithAlarm(int n, void **pp){
if( mem0.alarmCallback!=0 ){
int nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
if( nUsed+nFull >= mem0.alarmThreshold ){
mem0.nearlyFull = 1;
sqlite3MallocAlarm(nFull);
}else{
mem0.nearlyFull = 0;
}
}
p = sqlite3GlobalConfig.m.xMalloc(nFull);
#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
if( p==0 && mem0.alarmCallback ){
sqlite3MallocAlarm(nFull);
p = sqlite3GlobalConfig.m.xMalloc(nFull);
}
#endif
if( p ){
nFull = sqlite3MallocSize(p);
sqlite3StatusAdd(SQLITE_STATUS_MEMORY_USED, nFull);