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Cleanup and performance enhancements for mini-lookaside.

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FossilOrigin-Name: 74805668430051032ae9b256c84e252755ee03075fc08293c948675ed40ec280
This commit is contained in:
drh
2019-12-13 15:48:21 +00:00
parent ee5b6dd393
commit e6068027ca
6 changed files with 112 additions and 52 deletions
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47
src/main.c
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@@ -684,6 +684,8 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
#ifndef SQLITE_OMIT_LOOKASIDE
void *pStart;
sqlite3_int64 szAlloc = sz*(sqlite3_int64)cnt;
int nBig; /* Number of full-size slots */
int nSm; /* Number smaller mini-slots */
if( sqlite3LookasideUsed(db,0)>0 ){
return SQLITE_BUSY;
@@ -708,56 +710,69 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
sqlite3BeginBenignMalloc();
pStart = sqlite3Malloc( szAlloc ); /* IMP: R-61949-35727 */
sqlite3EndBenignMalloc();
if( pStart ) cnt = sqlite3MallocSize(pStart)/sz;
if( pStart ) szAlloc = sqlite3MallocSize(pStart);
}else{
pStart = pBuf;
}
#ifndef SQLITE_OMIT_MINI_LOOKASIDE
if( sz>=MINI_SZ*3 ){
nBig = szAlloc/(3*MINI_SZ+sz);
nSm = (szAlloc - sz*nBig)/MINI_SZ;
}else if( sz>=MINI_SZ*2 ){
nBig = szAlloc/(MINI_SZ+sz);
nSm = (szAlloc - sz*nBig)/MINI_SZ;
}else
#endif /* SQLITE_OMIT_MINI_LOOKASIDE */
if( sz>0 ){
nBig = szAlloc/sz;
nSm = 0;
}else{
nBig = nSm = 0;
}
db->lookaside.pStart = pStart;
db->lookaside.pInit = 0;
db->lookaside.pFree = 0;
#ifndef SQLITE_OMIT_MINI_LOOKASIDE
db->lookaside.pMiniInit = 0;
db->lookaside.pMiniFree = 0;
/* The arithmetic below causes the number of large lookaside slots to be 1/3
** the number of mini slots, based on the observation that 75% of allocations
** are <= MINI_SZ bytes.
*/
cnt = szAlloc/(3*MINI_SZ+sz);
#endif
db->lookaside.sz = (u16)sz;
db->lookaside.szTrue = (u16)sz;
if( pStart ){
int i;
LookasideSlot *p;
assert( sz > (int)sizeof(LookasideSlot*) );
db->lookaside.nSlot = cnt;
p = (LookasideSlot*)pStart;
for(i=cnt-1; i>=0; i--){
for(i=0; i<nBig; i++){
p->pNext = db->lookaside.pInit;
db->lookaside.pInit = p;
p = (LookasideSlot*)&((u8*)p)[sz];
}
#ifndef SQLITE_OMIT_MINI_LOOKASIDE
db->lookaside.pMiniInit = 0;
db->lookaside.pMiniFree = 0;
db->lookaside.pMiddle = p;
/* Fill the remainder of the buffer with mini slots */
while(p<=(LookasideSlot*)&((u8*)pStart)[szAlloc-MINI_SZ]){
for(i=0; i<nSm; i++){
p->pNext = db->lookaside.pMiniInit;
db->lookaside.pMiniInit = p;
db->lookaside.nSlot++;
p = (LookasideSlot*)&((u8*)p)[MINI_SZ];
}
#endif
#endif /* SQLITE_OMIT_MINI_LOOKASIDE */
assert( ((uptr)p)<=szAlloc + (uptr)pStart );
db->lookaside.pEnd = p;
db->lookaside.bDisable = 0;
db->lookaside.bMalloced = pBuf==0 ?1:0;
db->lookaside.nSlot = nBig+nSm;
}else{
db->lookaside.pStart = db;
#ifndef SQLITE_OMIT_MINI_LOOKASIDE
db->lookaside.pMiniInit = 0;
db->lookaside.pMiniFree = 0;
db->lookaside.pMiddle = db;
#endif /* SQLITE_OMIT_MINI_LOOKASIDE */
db->lookaside.pEnd = db;
db->lookaside.bDisable = 1;
db->lookaside.sz = 0;
db->lookaside.bMalloced = 0;
db->lookaside.nSlot = 0;
}
assert( sqlite3LookasideUsed(db,0)==0 );
#endif /* SQLITE_OMIT_LOOKASIDE */
return SQLITE_OK;
}