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Performance optimizations in sqlite3PcacheFetch().

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FossilOrigin-Name: b60cc11ef775c23a2245d9e7a00dab34013f3ccb
This commit is contained in:
drh
2014-02-03 17:04:29 +00:00
parent e39a732ce2
commit fe21a796f7
3 changed files with 33 additions and 16 deletions
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34
src/pcache.c
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@@ -23,7 +23,8 @@ struct PCache {
int szCache; /* Configured cache size */
int szPage; /* Size of every page in this cache */
int szExtra; /* Size of extra space for each page */
int bPurgeable; /* True if pages are on backing store */
u8 bPurgeable; /* True if pages are on backing store */
u8 eCreate; /* eCreate value for for xFetch() */
int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */
void *pStress; /* Argument to xStress */
sqlite3_pcache *pCache; /* Pluggable cache module */
@@ -90,6 +91,10 @@ static void pcacheRemoveFromDirtyList(PgHdr *pPage){
}else{
assert( pPage==p->pDirty );
p->pDirty = pPage->pDirtyNext;
if( p->pDirty==0 && p->bPurgeable ){
assert( p->eCreate==1 );
p->eCreate = 2;
}
}
pPage->pDirtyNext = 0;
pPage->pDirtyPrev = 0;
@@ -110,6 +115,9 @@ static void pcacheAddToDirtyList(PgHdr *pPage){
if( pPage->pDirtyNext ){
assert( pPage->pDirtyNext->pDirtyPrev==0 );
pPage->pDirtyNext->pDirtyPrev = pPage;
}else if( p->bPurgeable ){
assert( p->eCreate==2 );
p->eCreate = 1;
}
p->pDirty = pPage;
if( !p->pDirtyTail ){
@@ -179,6 +187,7 @@ void sqlite3PcacheOpen(
p->szPage = szPage;
p->szExtra = szExtra;
p->bPurgeable = bPurgeable;
p->eCreate = 2;
p->xStress = xStress;
p->pStress = pStress;
p->szCache = 100;
@@ -218,7 +227,7 @@ int sqlite3PcacheFetch(
int createFlag, /* If true, create page if it does not exist already */
PgHdr **ppPage /* Write the page here */
){
sqlite3_pcache_page *pPage = 0;
sqlite3_pcache_page *pPage;
PgHdr *pPgHdr = 0;
int eCreate;
@@ -229,8 +238,12 @@ int sqlite3PcacheFetch(
/* If the pluggable cache (sqlite3_pcache*) has not been allocated,
** allocate it now.
*/
if( !pCache->pCache && createFlag ){
if( !pCache->pCache ){
sqlite3_pcache *p;
if( !createFlag ){
*ppPage = 0;
return SQLITE_OK;
}
p = sqlite3GlobalConfig.pcache2.xCreate(
pCache->szPage, pCache->szExtra + sizeof(PgHdr), pCache->bPurgeable
);
@@ -241,11 +254,16 @@ int sqlite3PcacheFetch(
pCache->pCache = p;
}
eCreate = createFlag * (1 + (!pCache->bPurgeable || !pCache->pDirty));
if( pCache->pCache ){
pPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);
}
/* eCreate defines what to do if the page does not exist.
** 0 Do not allocate a new page. (createFlag==0)
** 1 Allocate a new page if doing so is inexpensive.
** (createFlag==1 AND bPurgeable AND pDirty)
** 2 Allocate a new page even it doing so is difficult.
** (createFlag==1 AND !(bPurgeable AND pDirty)
*/
eCreate = createFlag==0 ? 0 : pCache->eCreate;
assert( (createFlag*(1+(!pCache->bPurgeable||!pCache->pDirty)))==eCreate );
pPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);
if( !pPage && eCreate==1 ){
PgHdr *pPg;