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Miscellaneous cleanup in the new pcache code. (CVS 5629)

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FossilOrigin-Name: da1777259f53c2e20c7ced06bf6f2a550f0ea0fc
This commit is contained in:
drh
2008-08-28 02:26:07 +00:00
parent 59633aeec2
commit a85f7e36e8
6 changed files with 183 additions and 151 deletions
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274
src/pcache.c
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@@ -11,30 +11,50 @@
*************************************************************************
** This file implements that page cache.
**
** @(#) $Id: pcache.c,v 1.18 2008/08/27 16:38:57 danielk1977 Exp $
** @(#) $Id: pcache.c,v 1.19 2008/08/28 02:26:07 drh Exp $
*/
#include "sqliteInt.h"
/*
** A complete page cache is an instance of this structure.
**
** A cache may only be deleted by its owner and while holding the
** SQLITE_MUTEX_STATUS_LRU mutex.
*/
struct PCache {
int szPage; /* Size of every page in this cache */
int szExtra; /* Size of extra space for each page */
int nHash; /* Number of slots in apHash[] */
int nPage; /* Total number of pages in apHash */
int nMax; /* Configured cache size */
int nMin; /* Configured minimum cache size */
PgHdr **apHash; /* Hash table for fast lookup by pgno */
int bPurgeable; /* True if pages are on backing store */
void (*xDestroy)(PgHdr*); /* Called when refcnt goes 1->0 */
int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */
void *pStress; /* Argument to xStress */
PgHdr *pClean; /* List of clean pages in use */
/*********************************************************************
** The first group of elements may be read or written at any time by
** the cache owner without holding the mutex. No thread other than the
** cache owner is permitted to access these elements at any time.
*/
PgHdr *pDirty, *pDirtyTail; /* List of dirty pages in LRU order */
PgHdr *pSynced; /* Last synced page in dirty page list */
int nRef; /* Number of pinned pages */
int nPinned; /* Number of pinned and/or dirty pages */
int nMax; /* Configured cache size */
int nMin; /* Configured minimum cache size */
/**********************************************************************
** The next group of elements are fixed when the cache is created and
** may not be changed afterwards. These elements can read at any time by
** the cache owner or by any thread holding the the mutex. Non-owner
** threads must hold the mutex when reading these elements to prevent
** the entire PCache object from being deleted during the read.
*/
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 */
void (*xDestroy)(PgHdr*); /* Called when refcnt goes 1->0 */
int (*xStress)(void*,PgHdr*); /* Call to try make a page clean */
void *pStress; /* Argument to xStress */
/**********************************************************************
** The final group of elements can only be accessed while holding the
** mutex. Both the cache owner and any other thread must hold the mutex
** to read or write any of these elements.
*/
int nPage; /* Total number of pages in apHash */
int nHash; /* Number of slots in apHash[] */
PgHdr **apHash; /* Hash table for fast lookup by pgno */
PgHdr *pClean; /* List of clean pages in use */
};
/*
@@ -47,20 +67,6 @@ struct PgFreeslot {
/*
** Global data for the page cache.
**
** The maximum number of cached pages stored by the system is determined
** by the pcache.mxPage and pcache.mxPagePurgeable variables. If
** mxPage is non-zero, then the system tries to limit the number of
** cached pages stored to mxPage. In this case mxPagePurgeable is not
** used.
**
** If mxPage is zero, then the system tries to limit the number of
** pages held by purgable caches to mxPagePurgeable.
**
** The doubly-linked list that runs between pcache.pLruHead and
** pcache.pLruTail contains all clean purgable pages in the system
** with a zero reference count. pcache.pLruTail is the next page to
** be recycled.
*/
static struct PCacheGlobal {
int isInit; /* True when initialized */
@@ -78,29 +84,46 @@ static struct PCacheGlobal {
} pcache = {0};
/*
** All global variables used by this module (most of which are grouped
** All global variables used by this module (all of which are grouped
** together in global structure "pcache" above) are protected by the static
** SQLITE_MUTEX_STATIC_LRU mutex. A pointer to this mutex is stored in
** variable "pcache.mutex".
**
** Access to the contents of the individual PCache structures is not
** protected. It is the job of the caller to ensure that these structures
** are accessed in a thread-safe manner.
** Some elements of the PCache and PgHdr structures are protected by the
** SQLITE_MUTEX_STATUS_LRU mutex and other are not. The protected
** elements are grouped at the end of the structures and are clearly
** marked.
**
** Use the following macros must surround all access (read or write)
** of protected elements. The mutex is not recursive and may not be
** entered more than once. The pcacheMutexHeld() macro should only be
** used within an assert() to verify that the mutex is being held.
*/
#define pcacheEnterMutex() sqlite3_mutex_enter(pcache.mutex)
#define pcacheExitMutex() sqlite3_mutex_leave(pcache.mutex)
#define pcacheMutexHeld() sqlite3_mutex_held(pcache.mutex)
#define pcacheEnterGlobal() sqlite3_mutex_enter(pcache.mutex)
#define pcacheExitGlobal() sqlite3_mutex_leave(pcache.mutex)
/*
** Some of the assert() macros in this code are too expensive to run
** even during normal debugging. Use them only rarely on long-running
** tests. Enable the expensive asserts using the
** -DSQLITE_ENABLE_EXPENSIVE_ASSERT=1 compile-time option.
*/
#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
# define expensive_assert(X) assert(X)
#else
# define expensive_assert(X)
#endif
/********************************** Linked List Management ********************/
#ifndef NDEBUG
#if !defined(NDEBUG) && defined(SQLITE_ENABLE_EXPENSIVE_ASSERT)
/*
** This routine verifies that the number of entries in the hash table
** is pCache->nPage. This routine is used within assert() statements
** only and is therefore disabled during production builds.
*/
static int pcacheCheckHashCount(PCache *pCache){
#if 0
int i;
int nPage = 0;
for(i=0; i<pCache->nHash; i++){
@@ -110,19 +133,20 @@ static int pcacheCheckHashCount(PCache *pCache){
}
}
assert( nPage==pCache->nPage );
#endif
return 1;
}
#endif /* !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT */
#if !defined(NDEBUG) && defined(SQLITE_ENABLE_EXPENSIVE_ASSERT)
/*
** Based on the current value of PCache.nRef and the contents of the
** PCache.pDirty list, return the expected value of the PCache.nPinned
** counter. This is only used in debugging builds, as follows:
**
** assert( pCache->nPinned==pcachePinnedCount(pCache) );
** expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
*/
static int pcachePinnedCount(PCache *pCache){
#if 0
PgHdr *p;
int nPinned = pCache->nRef;
for(p=pCache->pDirty; p; p=p->pNext){
@@ -131,34 +155,35 @@ static int pcachePinnedCount(PCache *pCache){
}
}
return nPinned;
#endif
return pCache->nPinned;
}
#endif /* !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT */
#if !defined(NDEBUG) && defined(SQLITE_ENABLE_EXPENSIVE_ASSERT)
/*
** Check that the pCache->pSynced variable is set correctly. If it
** is not, either fail an assert or return zero. Otherwise, return
** non-zero. This is only used in debugging builds, as follows:
**
** assert( pcacheCheckSynced(pCache) );
** expensive_assert( pcacheCheckSynced(pCache) );
*/
static int pcacheCheckSynced(PCache *pCache){
#if 0
PgHdr *p = pCache->pDirtyTail;
for(p=pCache->pDirtyTail; p!=pCache->pSynced; p=p->pPrev){
assert( p->nRef || (p->flags&PGHDR_NEED_SYNC) );
}
return (p==0 || p->nRef || (p->flags&PGHDR_NEED_SYNC)==0);
#endif
return 1;
}
#endif /* !NDEBUG && SQLITE_ENABLE_EXPENSIVE_ASSERT */
#endif
/*
** Remove a page from its hash table (PCache.apHash[]).
*/
static void pcacheRemoveFromHash(PgHdr *pPage){
/* assert( pcacheMutexHeld() ); *** FIXME ****/
if( pPage->pPrevHash ){
pPage->pPrevHash->pNextHash = pPage->pNextHash;
}else{
@@ -171,15 +196,18 @@ static void pcacheRemoveFromHash(PgHdr *pPage){
pPage->pNextHash->pPrevHash = pPage->pPrevHash;
}
pPage->pCache->nPage--;
assert( pcacheCheckHashCount(pPage->pCache) );
expensive_assert( pcacheCheckHashCount(pPage->pCache) );
}
/*
** Insert a page into the hash table
**
** The mutex must be held by the caller.
*/
static void pcacheAddToHash(PgHdr *pPage){
PCache *pCache = pPage->pCache;
u32 h = pPage->pgno % pCache->nHash;
/* assert( pcacheMutexHeld() ); *** FIXME *****/
pPage->pNextHash = pCache->apHash[h];
pPage->pPrevHash = 0;
if( pCache->apHash[h] ){
@@ -187,7 +215,7 @@ static void pcacheAddToHash(PgHdr *pPage){
}
pCache->apHash[h] = pPage;
pCache->nPage++;
assert( pcacheCheckHashCount(pCache) );
expensive_assert( pcacheCheckHashCount(pCache) );
}
/*
@@ -195,29 +223,29 @@ static void pcacheAddToHash(PgHdr *pPage){
** at least nHash buckets.
*/
static int pcacheResizeHash(PCache *pCache, int nHash){
PgHdr *p;
PgHdr **pNew;
/* assert( pcacheMutexHeld() ); **** FIXME *****/
#ifdef SQLITE_MALLOC_SOFT_LIMIT
if( nHash*sizeof(PgHdr*)>SQLITE_MALLOC_SOFT_LIMIT ){
nHash = SQLITE_MALLOC_SOFT_LIMIT/sizeof(PgHdr *);
}
#endif
if( nHash>pCache->nHash ){
PgHdr *p;
PgHdr **pNew = (PgHdr **)sqlite3_malloc(sizeof(PgHdr*)*nHash);
if( !pNew ){
return SQLITE_NOMEM;
}
memset(pNew, 0, sizeof(PgHdr *)*nHash);
sqlite3_free(pCache->apHash);
pCache->apHash = pNew;
pCache->nHash = nHash;
pCache->nPage = 0;
for(p=pCache->pClean; p; p=p->pNext){
pcacheAddToHash(p);
}
for(p=pCache->pDirty; p; p=p->pNext){
pcacheAddToHash(p);
}
pNew = (PgHdr **)sqlite3_malloc(sizeof(PgHdr*)*nHash);
if( !pNew ){
return SQLITE_NOMEM;
}
memset(pNew, 0, sizeof(PgHdr *)*nHash);
sqlite3_free(pCache->apHash);
pCache->apHash = pNew;
pCache->nHash = nHash;
pCache->nPage = 0;
for(p=pCache->pClean; p; p=p->pNext){
pcacheAddToHash(p);
}
for(p=pCache->pDirty; p; p=p->pNext){
pcacheAddToHash(p);
}
return SQLITE_OK;
}
@@ -229,6 +257,7 @@ static int pcacheResizeHash(PCache *pCache, int nHash){
static void pcacheRemoveFromList(PgHdr **ppHead, PgHdr *pPage){
int isDirtyList = (ppHead==&pPage->pCache->pDirty);
assert( ppHead==&pPage->pCache->pClean || ppHead==&pPage->pCache->pDirty );
/* assert( pcacheMutexHeld() || ppHead!=&pPage->pCache->pClean ); *** FIXME */
if( pPage->pPrev ){
pPage->pPrev->pNext = pPage->pNext;
@@ -384,13 +413,11 @@ void *pcacheMalloc(int sz, PCache *pCache){
** global pcache mutex and unlock the pager-cache object pCache. This is
** so that if the attempt to allocate a new buffer causes the the
** configured soft-heap-limit to be breached, it will be possible to
** reclaim memory from this pager-cache. Because sqlite3PcacheLock()
** might block on the MEM2 mutex, it has to be called before re-entering
** the global LRU mutex.
** reclaim memory from this pager-cache.
*/
pcacheExitGlobal();
pcacheExitMutex();
p = sqlite3Malloc(sz);
pcacheEnterGlobal();
pcacheEnterMutex();
if( p ){
sz = sqlite3MallocSize(p);
@@ -401,9 +428,9 @@ void *pcacheMalloc(int sz, PCache *pCache){
}
void *sqlite3PageMalloc(sz){
void *p;
pcacheEnterGlobal();
pcacheEnterMutex();
p = pcacheMalloc(sz, 0);
pcacheExitGlobal();
pcacheExitMutex();
return p;
}
@@ -426,9 +453,9 @@ void pcacheFree(void *p){
}
}
void sqlite3PageFree(void *p){
pcacheEnterGlobal();
pcacheEnterMutex();
pcacheFree(p);
pcacheExitGlobal();
pcacheExitMutex();
}
/*
@@ -519,14 +546,14 @@ static int pcacheRecycleOrAlloc(PCache *pCache, PgHdr **ppPage){
assert( sqlite3_mutex_notheld(pcache.mutex) );
*ppPage = 0;
pcacheEnterGlobal();
pcacheEnterMutex();
/* If we have reached the limit for pinned/dirty pages, and there is at
** least one dirty page, invoke the xStress callback to cause a page to
** become clean.
*/
assert( pCache->nPinned==pcachePinnedCount(pCache) );
assert( pcacheCheckSynced(pCache) );
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
expensive_assert( pcacheCheckSynced(pCache) );
if( pCache->xStress
&& pCache->pDirty
&& pCache->nPinned>=(pcache.nMaxPage+pCache->nMin-pcache.nMinPage)
@@ -543,12 +570,12 @@ static int pcacheRecycleOrAlloc(PCache *pCache, PgHdr **ppPage){
}
if( pPg ){
int rc;
pcacheExitGlobal();
pcacheExitMutex();
rc = pCache->xStress(pCache->pStress, pPg);
if( rc!=SQLITE_OK ){
return rc;
}
pcacheEnterGlobal();
pcacheEnterMutex();
}
}
@@ -558,7 +585,7 @@ static int pcacheRecycleOrAlloc(PCache *pCache, PgHdr **ppPage){
}
/* If a page has been recycled but it is the wrong size, free it. */
if( p && (p->pCache->szPage!=szPage || p->pCache->szExtra!=szExtra) ){
if( p && (p->pCache->szPage!=szPage || p->pCache->szPage!=szExtra) ){
pcachePageFree(p);
p = 0;
}
@@ -567,7 +594,7 @@ static int pcacheRecycleOrAlloc(PCache *pCache, PgHdr **ppPage){
p = pcachePageAlloc(pCache);
}
pcacheExitGlobal();
pcacheExitMutex();
*ppPage = p;
return (p?SQLITE_OK:SQLITE_NOMEM);
}
@@ -622,13 +649,13 @@ void sqlite3PcacheOpen(
p->nMax = 100;
p->nMin = 10;
pcacheEnterGlobal();
pcacheEnterMutex();
if( bPurgeable ){
pcache.nMaxPage += p->nMax;
pcache.nMinPage += p->nMin;
}
pcacheExitGlobal();
pcacheExitMutex();
}
/*
@@ -653,7 +680,7 @@ int sqlite3PcacheFetch(
assert( pcache.isInit );
assert( pCache!=0 );
assert( pgno>0 );
assert( pCache->nPinned==pcachePinnedCount(pCache) );
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
/* Search the hash table for the requested page. Exit early if it is found. */
if( pCache->apHash ){
@@ -662,9 +689,9 @@ int sqlite3PcacheFetch(
if( pPage->pgno==pgno ){
if( pPage->nRef==0 ){
if( 0==(pPage->flags&PGHDR_DIRTY) ){
pcacheEnterGlobal();
pcacheEnterMutex();
pcacheRemoveFromLruList(pPage);
pcacheExitGlobal();
pcacheExitMutex();
pCache->nPinned++;
}
pCache->nRef++;
@@ -679,7 +706,7 @@ int sqlite3PcacheFetch(
if( createFlag ){
int rc = SQLITE_OK;
if( pCache->nHash<=pCache->nPage ){
rc = pcacheResizeHash(pCache, pCache->nHash<256?256:pCache->nHash*2);
rc = pcacheResizeHash(pCache, pCache->nHash<256 ? 256 : pCache->nHash*2);
if( rc!=SQLITE_OK ){
return rc;
}
@@ -704,7 +731,7 @@ int sqlite3PcacheFetch(
*ppPage = 0;
}
assert( pCache->nPinned==pcachePinnedCount(pCache) );
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
return SQLITE_OK;
}
@@ -723,9 +750,9 @@ void sqlite3PcacheRelease(PgHdr *p){
pCache->nRef--;
if( (p->flags&PGHDR_DIRTY)==0 ){
pCache->nPinned--;
pcacheEnterGlobal();
pcacheEnterMutex();
pcacheAddToLruList(p);
pcacheExitGlobal();
pcacheExitMutex();
}else{
/* Move the page to the head of the caches dirty list. */
pcacheRemoveFromList(&pCache->pDirty, p);
@@ -753,9 +780,9 @@ void sqlite3PcacheDrop(PgHdr *p){
pCache->nPinned--;
pcacheRemoveFromList(&pCache->pClean, p);
pcacheRemoveFromHash(p);
pcacheEnterGlobal();
pcacheEnterMutex();
pcachePageFree(p);
pcacheExitGlobal();
pcacheExitMutex();
}
/*
@@ -785,15 +812,15 @@ void sqlite3PcacheMakeClean(PgHdr *p){
assert( p->flags & PGHDR_DIRTY );
pCache = p->pCache;
pcacheRemoveFromList(&pCache->pDirty, p);
pcacheEnterGlobal();
pcacheEnterMutex();
pcacheAddToList(&pCache->pClean, p);
p->flags &= ~PGHDR_DIRTY;
if( p->nRef==0 ){
pcacheAddToLruList(p);
pCache->nPinned--;
}
assert( pCache->nPinned==pcachePinnedCount(pCache) );
pcacheExitGlobal();
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
pcacheExitMutex();
}
/*
@@ -801,7 +828,7 @@ void sqlite3PcacheMakeClean(PgHdr *p){
*/
void sqlite3PcacheCleanAll(PCache *pCache){
PgHdr *p;
pcacheEnterGlobal();
pcacheEnterMutex();
while( (p = pCache->pDirty)!=0 ){
assert( p->apSave[0]==0 && p->apSave[1]==0 );
pcacheRemoveFromList(&pCache->pDirty, p);
@@ -813,8 +840,8 @@ void sqlite3PcacheCleanAll(PCache *pCache){
}
}
sqlite3PcacheAssertFlags(pCache, 0, PGHDR_DIRTY);
assert( pCache->nPinned==pcachePinnedCount(pCache) );
pcacheExitGlobal();
expensive_assert( pCache->nPinned==pcachePinnedCount(pCache) );
pcacheExitMutex();
}
/*
@@ -828,10 +855,10 @@ void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
p->pgno = newPgno;
if( newPgno==0 ){
p->flags |= PGHDR_REUSE_UNLIKELY;
pcacheEnterGlobal();
pcacheEnterMutex();
pcacheFree(p->apSave[0]);
pcacheFree(p->apSave[1]);
pcacheExitGlobal();
pcacheExitMutex();
p->apSave[0] = 0;
p->apSave[1] = 0;
sqlite3PcacheMakeClean(p);
@@ -869,7 +896,7 @@ void pcacheClear(PCache *pCache){
void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
PgHdr *p, *pNext;
PgHdr *pDirty = pCache->pDirty;
pcacheEnterGlobal();
pcacheEnterMutex();
for(p=pCache->pClean; p||pDirty; p=pNext){
if( !p ){
p = pDirty;
@@ -895,7 +922,7 @@ void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
}
}
}
pcacheExitGlobal();
pcacheExitMutex();
}
@@ -903,7 +930,7 @@ void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
** Close a cache.
*/
void sqlite3PcacheClose(PCache *pCache){
pcacheEnterGlobal();
pcacheEnterMutex();
/* Free all the pages used by this pager and remove them from the LRU list. */
pcacheClear(pCache);
@@ -913,12 +940,14 @@ void sqlite3PcacheClose(PCache *pCache){
}
sqlite3_free(pCache->apHash);
pcacheExitGlobal();
pcacheExitMutex();
}
/*
** Preserve the content of the page, if it has not been preserved
** already. If idJournal==0 then this is for the overall transaction.
** Preserve the content of the page. It is assumed that the content
** has not been preserved already.
**
** If idJournal==0 then this is for the overall transaction.
** If idJournal==1 then this is for the statement journal.
**
** This routine is used for in-memory databases only.
@@ -929,12 +958,11 @@ int sqlite3PcachePreserve(PgHdr *p, int idJournal){
void *x;
int sz;
assert( p->pCache->bPurgeable==0 );
if( !p->apSave[idJournal] ){
sz = p->pCache->szPage;
p->apSave[idJournal] = x = sqlite3PageMalloc( sz );
if( x==0 ) return SQLITE_NOMEM;
memcpy(x, p->pData, sz);
}
assert( p->apSave[idJournal]==0 );
sz = p->pCache->szPage;
p->apSave[idJournal] = x = sqlite3PageMalloc( sz );
if( x==0 ) return SQLITE_NOMEM;
memcpy(x, p->pData, sz);
return SQLITE_OK;
}
@@ -943,14 +971,14 @@ int sqlite3PcachePreserve(PgHdr *p, int idJournal){
*/
void sqlite3PcacheCommit(PCache *pCache, int idJournal){
PgHdr *p;
pcacheEnterGlobal(); /* Mutex is required to call pcacheFree() */
pcacheEnterMutex(); /* Mutex is required to call pcacheFree() */
for(p=pCache->pDirty; p; p=p->pNext){
if( p->apSave[idJournal] ){
pcacheFree(p->apSave[idJournal]);
p->apSave[idJournal] = 0;
}
}
pcacheExitGlobal();
pcacheExitMutex();
}
/*
@@ -959,7 +987,7 @@ void sqlite3PcacheCommit(PCache *pCache, int idJournal){
void sqlite3PcacheRollback(PCache *pCache, int idJournal){
PgHdr *p;
int sz;
pcacheEnterGlobal(); /* Mutex is required to call pcacheFree() */
pcacheEnterMutex(); /* Mutex is required to call pcacheFree() */
sz = pCache->szPage;
for(p=pCache->pDirty; p; p=p->pNext){
if( p->apSave[idJournal] ){
@@ -968,7 +996,7 @@ void sqlite3PcacheRollback(PCache *pCache, int idJournal){
p->apSave[idJournal] = 0;
}
}
pcacheExitGlobal();
pcacheExitMutex();
}
/*
@@ -991,9 +1019,9 @@ void sqlite3PcacheAssertFlags(PCache *pCache, int trueMask, int falseMask){
*/
int sqlite3PcacheClear(PCache *pCache){
assert(pCache->nRef==0);
pcacheEnterGlobal();
pcacheEnterMutex();
pcacheClear(pCache);
pcacheExitGlobal();
pcacheExitMutex();
return SQLITE_OK;
}
@@ -1125,7 +1153,7 @@ void sqlite3PcacheSetFlags(PCache *pCache, int andMask, int orMask){
/* Obtain the global mutex before modifying any PgHdr.flags variables
** or traversing the LRU list.
*/
pcacheEnterGlobal();
pcacheEnterMutex();
for(p=pCache->pDirty; p; p=p->pNext){
p->flags = (p->flags&andMask)|orMask;
@@ -1139,7 +1167,7 @@ void sqlite3PcacheSetFlags(PCache *pCache, int andMask, int orMask){
assert( !pCache->pSynced || (pCache->pSynced->flags&PGHDR_NEED_SYNC)==0 );
}
pcacheExitGlobal();
pcacheExitMutex();
}
/*
@@ -1157,10 +1185,10 @@ void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
mxPage = 10;
}
if( pCache->bPurgeable ){
pcacheEnterGlobal();
pcacheEnterMutex();
pcache.nMaxPage -= pCache->nMax;
pcache.nMaxPage += mxPage;
pcacheExitGlobal();
pcacheExitMutex();
}
pCache->nMax = mxPage;
}
@@ -1179,12 +1207,12 @@ int sqlite3PcacheReleaseMemory(int nReq){
int nFree = 0;
if( pcache.pStart==0 ){
PgHdr *p;
pcacheEnterGlobal();
pcacheEnterMutex();
while( (nReq<0 || nFree<nReq) && (p=pcacheRecyclePage()) ){
nFree += pcachePageSize(p);
pcachePageFree(p);
}
pcacheExitGlobal();
pcacheExitMutex();
}
return nFree;
}