SQLite

Check-in [b60cc11ef7]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Performance optimizations in sqlite3PcacheFetch().
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: b60cc11ef775c23a2245d9e7a00dab34013f3ccb
User & Date: drh 2014-02-03 17:04:29.099
Context
2014-02-04
15:55
Rearrange fields in the Parse object for a tighter packing, resulting in an 8% size reduction on x64. (check-in: 3e1a3f68d7 user: drh tags: trunk)
2014-02-03
17:04
Performance optimizations in sqlite3PcacheFetch(). (check-in: b60cc11ef7 user: drh tags: trunk)
14:04
Provide hints to the btree layer Next and Previous primitives to let them know if they can be no-ops if the underlying index is unique. (check-in: 6c643e45c2 user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/pcache.c.
19
20
21
22
23
24
25
26

27
28
29
30
31
32
33
struct PCache {
  PgHdr *pDirty, *pDirtyTail;         /* List of dirty pages in LRU order */
  PgHdr *pSynced;                     /* Last synced page in dirty page list */
  int nRef;                           /* Number of referenced pages */
  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 */

  int (*xStress)(void*,PgHdr*);       /* Call to try make a page clean */
  void *pStress;                      /* Argument to xStress */
  sqlite3_pcache *pCache;             /* Pluggable cache module */
  PgHdr *pPage1;                      /* Reference to page 1 */
};

/*







|
>







19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
struct PCache {
  PgHdr *pDirty, *pDirtyTail;         /* List of dirty pages in LRU order */
  PgHdr *pSynced;                     /* Last synced page in dirty page list */
  int nRef;                           /* Number of referenced pages */
  int szCache;                        /* Configured cache size */
  int szPage;                         /* Size of every page in this cache */
  int szExtra;                        /* Size of extra space for each page */
  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 */
  PgHdr *pPage1;                      /* Reference to page 1 */
};

/*
86
87
88
89
90
91
92




93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112



113
114
115
116
117
118
119
    p->pDirtyTail = pPage->pDirtyPrev;
  }
  if( pPage->pDirtyPrev ){
    pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
  }else{
    assert( pPage==p->pDirty );
    p->pDirty = pPage->pDirtyNext;




  }
  pPage->pDirtyNext = 0;
  pPage->pDirtyPrev = 0;

  expensive_assert( pcacheCheckSynced(p) );
}

/*
** Add page pPage to the head of the dirty list (PCache1.pDirty is set to
** pPage).
*/
static void pcacheAddToDirtyList(PgHdr *pPage){
  PCache *p = pPage->pCache;

  assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );

  pPage->pDirtyNext = p->pDirty;
  if( pPage->pDirtyNext ){
    assert( pPage->pDirtyNext->pDirtyPrev==0 );
    pPage->pDirtyNext->pDirtyPrev = pPage;



  }
  p->pDirty = pPage;
  if( !p->pDirtyTail ){
    p->pDirtyTail = pPage;
  }
  if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){
    p->pSynced = pPage;







>
>
>
>




















>
>
>







87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
    p->pDirtyTail = pPage->pDirtyPrev;
  }
  if( pPage->pDirtyPrev ){
    pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
  }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;

  expensive_assert( pcacheCheckSynced(p) );
}

/*
** Add page pPage to the head of the dirty list (PCache1.pDirty is set to
** pPage).
*/
static void pcacheAddToDirtyList(PgHdr *pPage){
  PCache *p = pPage->pCache;

  assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );

  pPage->pDirtyNext = p->pDirty;
  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 ){
    p->pDirtyTail = pPage;
  }
  if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){
    p->pSynced = pPage;
175
176
177
178
179
180
181

182
183
184
185
186
187
188
  void *pStress,               /* Argument to xStress */
  PCache *p                    /* Preallocated space for the PCache */
){
  memset(p, 0, sizeof(PCache));
  p->szPage = szPage;
  p->szExtra = szExtra;
  p->bPurgeable = bPurgeable;

  p->xStress = xStress;
  p->pStress = pStress;
  p->szCache = 100;
}

/*
** Change the page size for PCache object. The caller must ensure that there







>







183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
  void *pStress,               /* Argument to xStress */
  PCache *p                    /* Preallocated space for the PCache */
){
  memset(p, 0, sizeof(PCache));
  p->szPage = szPage;
  p->szExtra = szExtra;
  p->bPurgeable = bPurgeable;
  p->eCreate = 2;
  p->xStress = xStress;
  p->pStress = pStress;
  p->szCache = 100;
}

/*
** Change the page size for PCache object. The caller must ensure that there
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233




234
235
236
237
238
239
240
241
242
243







244
245
246
247
248
249
250
251
252
253
254
255
*/
int sqlite3PcacheFetch(
  PCache *pCache,       /* Obtain the page from this cache */
  Pgno pgno,            /* Page number to obtain */
  int createFlag,       /* If true, create page if it does not exist already */
  PgHdr **ppPage        /* Write the page here */
){
  sqlite3_pcache_page *pPage = 0;
  PgHdr *pPgHdr = 0;
  int eCreate;

  assert( pCache!=0 );
  assert( createFlag==1 || createFlag==0 );
  assert( pgno>0 );

  /* If the pluggable cache (sqlite3_pcache*) has not been allocated,
  ** allocate it now.
  */
  if( !pCache->pCache && createFlag ){
    sqlite3_pcache *p;




    p = sqlite3GlobalConfig.pcache2.xCreate(
        pCache->szPage, pCache->szExtra + sizeof(PgHdr), pCache->bPurgeable
    );
    if( !p ){
      return SQLITE_NOMEM;
    }
    sqlite3GlobalConfig.pcache2.xCachesize(p, numberOfCachePages(pCache));
    pCache->pCache = p;
  }








  eCreate = createFlag * (1 + (!pCache->bPurgeable || !pCache->pDirty));
  if( pCache->pCache ){
    pPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);
  }

  if( !pPage && eCreate==1 ){
    PgHdr *pPg;

    /* Find a dirty page to write-out and recycle. First try to find a 
    ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
    ** cleared), but if that is not possible settle for any other 
    ** unreferenced dirty page.







|










|

>
>
>
>










>
>
>
>
>
>
>
|
|
|
<
<







223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266


267
268
269
270
271
272
273
*/
int sqlite3PcacheFetch(
  PCache *pCache,       /* Obtain the page from this cache */
  Pgno pgno,            /* Page number to obtain */
  int createFlag,       /* If true, create page if it does not exist already */
  PgHdr **ppPage        /* Write the page here */
){
  sqlite3_pcache_page *pPage;
  PgHdr *pPgHdr = 0;
  int eCreate;

  assert( pCache!=0 );
  assert( createFlag==1 || createFlag==0 );
  assert( pgno>0 );

  /* If the pluggable cache (sqlite3_pcache*) has not been allocated,
  ** allocate it now.
  */
  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
    );
    if( !p ){
      return SQLITE_NOMEM;
    }
    sqlite3GlobalConfig.pcache2.xCachesize(p, numberOfCachePages(pCache));
    pCache->pCache = p;
  }

  /* 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;

    /* Find a dirty page to write-out and recycle. First try to find a 
    ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
    ** cleared), but if that is not possible settle for any other 
    ** unreferenced dirty page.