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Overview
Comment:Rename the PCache1.mxPinned field to n90pct (since it is 90% of nMax) in order to distinguish it from PGroup.mxPinned. Fix the computation of n90pct so that it does not overflow adversely on excessively large cache sizes.
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SHA1:c85202baac49b22a4be36b9733d44f01d83edb28
User & Date: drh 2011-01-26 00:07:03
Context
2011-01-26
06:13
Changes to exclusive2.test to make it more deterministic. check-in: 84b0c2bc user: dan tags: trunk
00:07
Rename the PCache1.mxPinned field to n90pct (since it is 90% of nMax) in order to distinguish it from PGroup.mxPinned. Fix the computation of n90pct so that it does not overflow adversely on excessively large cache sizes. check-in: c85202ba user: drh tags: trunk
2011-01-25
18:30
Fix new compiler warnings in pcache1.c that were introduced by the recent performance enhancement patches of [e14649301138b684]. check-in: c17703ec user: drh tags: trunk
Changes
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Changes to src/pcache1.c.

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  ** The PGroup mutex must be held when accessing nMax.
  */
  PGroup *pGroup;                     /* PGroup this cache belongs to */
  int szPage;                         /* Size of allocated pages in bytes */
  int bPurgeable;                     /* True if cache is purgeable */
  unsigned int nMin;                  /* Minimum number of pages reserved */
  unsigned int nMax;                  /* Configured "cache_size" value */
  unsigned int mxPinned;              /* nMax*9/10 */

  /* Hash table of all pages. The following variables may only be accessed
  ** when the accessor is holding the PGroup mutex.
  */
  unsigned int nRecyclable;           /* Number of pages in the LRU list */
  unsigned int nPage;                 /* Total number of pages in apHash */
  unsigned int nHash;                 /* Number of slots in apHash[] */
................................................................................
  PCache1 *pCache = (PCache1 *)p;
  if( pCache->bPurgeable ){
    PGroup *pGroup = pCache->pGroup;
    pcache1EnterMutex(pGroup);
    pGroup->nMaxPage += (nMax - pCache->nMax);
    pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
    pCache->nMax = nMax;
    pCache->mxPinned = nMax*9/10;
    pcache1EnforceMaxPage(pGroup);
    pcache1LeaveMutex(pGroup);
  }
}

/*
** Implementation of the sqlite3_pcache.xPagecount method. 
................................................................................
#ifdef SQLITE_MUTEX_OMIT
  pGroup = pCache->pGroup;
#endif


  /* Step 3: Abort if createFlag is 1 but the cache is nearly full */
  nPinned = pCache->nPage - pCache->nRecyclable;

  assert( pGroup->mxPinned == pGroup->nMaxPage + 10 - pGroup->nMinPage );
  assert( pCache->mxPinned == pCache->nMax*9/10 );
  if( createFlag==1 && (
        nPinned>=pGroup->mxPinned
     || nPinned>=(int)pCache->mxPinned
     || pcache1UnderMemoryPressure(pCache)
  )){
    goto fetch_out;
  }

  if( pCache->nPage>=pCache->nHash && pcache1ResizeHash(pCache) ){
    goto fetch_out;







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  ** The PGroup mutex must be held when accessing nMax.
  */
  PGroup *pGroup;                     /* PGroup this cache belongs to */
  int szPage;                         /* Size of allocated pages in bytes */
  int bPurgeable;                     /* True if cache is purgeable */
  unsigned int nMin;                  /* Minimum number of pages reserved */
  unsigned int nMax;                  /* Configured "cache_size" value */
  unsigned int n90pct;                /* nMax*9/10 */

  /* Hash table of all pages. The following variables may only be accessed
  ** when the accessor is holding the PGroup mutex.
  */
  unsigned int nRecyclable;           /* Number of pages in the LRU list */
  unsigned int nPage;                 /* Total number of pages in apHash */
  unsigned int nHash;                 /* Number of slots in apHash[] */
................................................................................
  PCache1 *pCache = (PCache1 *)p;
  if( pCache->bPurgeable ){
    PGroup *pGroup = pCache->pGroup;
    pcache1EnterMutex(pGroup);
    pGroup->nMaxPage += (nMax - pCache->nMax);
    pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
    pCache->nMax = nMax;
    pCache->n90pct = pCache->nMax*9/10;
    pcache1EnforceMaxPage(pGroup);
    pcache1LeaveMutex(pGroup);
  }
}

/*
** Implementation of the sqlite3_pcache.xPagecount method. 
................................................................................
#ifdef SQLITE_MUTEX_OMIT
  pGroup = pCache->pGroup;
#endif


  /* Step 3: Abort if createFlag is 1 but the cache is nearly full */
  nPinned = pCache->nPage - pCache->nRecyclable;
  assert( nPinned>=0 );
  assert( pGroup->mxPinned == pGroup->nMaxPage + 10 - pGroup->nMinPage );
  assert( pCache->n90pct == pCache->nMax*9/10 );
  if( createFlag==1 && (
        nPinned>=pGroup->mxPinned
     || nPinned>=(int)pCache->n90pct
     || pcache1UnderMemoryPressure(pCache)
  )){
    goto fetch_out;
  }

  if( pCache->nPage>=pCache->nHash && pcache1ResizeHash(pCache) ){
    goto fetch_out;