ext/misc/pcachetrace.c

   1 /*
   2 ** 2023-06-21
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 *************************************************************************
  12 **
  13 ** This file implements an extension that uses the SQLITE_CONFIG_PCACHE2
  14 ** mechanism to add a tracing layer on top of pluggable page cache of
  15 ** SQLite.  If this extension is registered prior to sqlite3_initialize(),
  16 ** it will cause all page cache activities to be logged on standard output,
  17 ** or to some other FILE specified by the initializer.
  18 **
  19 ** This file needs to be compiled into the application that uses it.
  20 **
  21 ** This extension is used to implement the --pcachetrace option of the
  22 ** command-line shell.
  23 */
  24 #include <assert.h>
  25 #include <string.h>
  26 #include <stdio.h>
  27
  28 /* The original page cache routines */
  29 static sqlite3_pcache_methods2 pcacheBase;
  30 static FILE *pcachetraceOut;
  31
  32 /* Methods that trace pcache activity */
  33 static int pcachetraceInit(void *pArg){
  34   int nRes;
  35   if( pcachetraceOut ){
  36     fprintf(pcachetraceOut, "PCACHETRACE: xInit(%p)\n", pArg);
  37   }
  38   nRes = pcacheBase.xInit(pArg);
  39   if( pcachetraceOut ){
  40     fprintf(pcachetraceOut, "PCACHETRACE: xInit(%p) -> %d\n", pArg, nRes);
  41   }
  42   return nRes;
  43 }
  44 static void pcachetraceShutdown(void *pArg){
  45   if( pcachetraceOut ){
  46     fprintf(pcachetraceOut, "PCACHETRACE: xShutdown(%p)\n", pArg);
  47   }
  48   pcacheBase.xShutdown(pArg);
  49 }
  50 static sqlite3_pcache *pcachetraceCreate(int szPage, int szExtra, int bPurge){
  51   sqlite3_pcache *pRes;
  52   if( pcachetraceOut ){
  53     fprintf(pcachetraceOut, "PCACHETRACE: xCreate(%d,%d,%d)\n",
  54             szPage, szExtra, bPurge);
  55   }
  56   pRes = pcacheBase.xCreate(szPage, szExtra, bPurge);
  57   if( pcachetraceOut ){
  58     fprintf(pcachetraceOut, "PCACHETRACE: xCreate(%d,%d,%d) -> %p\n",
  59             szPage, szExtra, bPurge, pRes);
  60   }
  61   return pRes;
  62 }
  63 static void pcachetraceCachesize(sqlite3_pcache *p, int nCachesize){
  64   if( pcachetraceOut ){
  65     fprintf(pcachetraceOut, "PCACHETRACE: xCachesize(%p, %d)\n", p, nCachesize);
  66   }
  67   pcacheBase.xCachesize(p, nCachesize);
  68 }
  69 static int pcachetracePagecount(sqlite3_pcache *p){
  70   int nRes;
  71   if( pcachetraceOut ){
  72     fprintf(pcachetraceOut, "PCACHETRACE: xPagecount(%p)\n", p);
  73   }
  74   nRes = pcacheBase.xPagecount(p);
  75   if( pcachetraceOut ){
  76     fprintf(pcachetraceOut, "PCACHETRACE: xPagecount(%p) -> %d\n", p, nRes);
  77   }
  78   return nRes;
  79 }
  80 static sqlite3_pcache_page *pcachetraceFetch(
  81   sqlite3_pcache *p,
  82   unsigned key,
  83   int crFg
  84 ){
  85   sqlite3_pcache_page *pRes;
  86   if( pcachetraceOut ){
  87     fprintf(pcachetraceOut, "PCACHETRACE: xFetch(%p,%u,%d)\n", p, key, crFg);
  88   }
  89   pRes = pcacheBase.xFetch(p, key, crFg);
  90   if( pcachetraceOut ){
  91     fprintf(pcachetraceOut, "PCACHETRACE: xFetch(%p,%u,%d) -> %p\n",
  92             p, key, crFg, pRes);
  93   }
  94   return pRes;
  95 }
  96 static void pcachetraceUnpin(
  97   sqlite3_pcache *p,
  98   sqlite3_pcache_page *pPg,
  99   int bDiscard
 100 ){
 101   if( pcachetraceOut ){
 102     fprintf(pcachetraceOut, "PCACHETRACE: xUnpin(%p, %p, %d)\n",
 103             p, pPg, bDiscard);
 104   }
 105   pcacheBase.xUnpin(p, pPg, bDiscard);
 106 }
 107 static void pcachetraceRekey(
 108   sqlite3_pcache *p,
 109   sqlite3_pcache_page *pPg,
 110   unsigned oldKey,
 111   unsigned newKey
 112 ){
 113   if( pcachetraceOut ){
 114     fprintf(pcachetraceOut, "PCACHETRACE: xRekey(%p, %p, %u, %u)\n",
 115         p, pPg, oldKey, newKey);
 116   }
 117   pcacheBase.xRekey(p, pPg, oldKey, newKey);
 118 }
 119 static void pcachetraceTruncate(sqlite3_pcache *p, unsigned n){
 120   if( pcachetraceOut ){
 121     fprintf(pcachetraceOut, "PCACHETRACE: xTruncate(%p, %u)\n", p, n);
 122   }
 123   pcacheBase.xTruncate(p, n);
 124 }
 125 static void pcachetraceDestroy(sqlite3_pcache *p){
 126   if( pcachetraceOut ){
 127     fprintf(pcachetraceOut, "PCACHETRACE: xDestroy(%p)\n", p);
 128   }
 129   pcacheBase.xDestroy(p);
 130 }
 131 static void pcachetraceShrink(sqlite3_pcache *p){
 132   if( pcachetraceOut ){
 133     fprintf(pcachetraceOut, "PCACHETRACE: xShrink(%p)\n", p);
 134   }
 135   pcacheBase.xShrink(p);
 136 }
 137
 138 /* The substitute pcache methods */
 139 static sqlite3_pcache_methods2 ersaztPcacheMethods = {
 140   0,
 141   0,
 142   pcachetraceInit,
 143   pcachetraceShutdown,
 144   pcachetraceCreate,
 145   pcachetraceCachesize,
 146   pcachetracePagecount,
 147   pcachetraceFetch,
 148   pcachetraceUnpin,
 149   pcachetraceRekey,
 150   pcachetraceTruncate,
 151   pcachetraceDestroy,
 152   pcachetraceShrink
 153 };
 154
 155 /* Begin tracing memory allocations to out. */
 156 int sqlite3PcacheTraceActivate(FILE *out){
 157   int rc = SQLITE_OK;
 158   if( pcacheBase.xFetch==0 ){
 159     rc = sqlite3_config(SQLITE_CONFIG_GETPCACHE2, &pcacheBase);
 160     if( rc==SQLITE_OK ){
 161       rc = sqlite3_config(SQLITE_CONFIG_PCACHE2, &ersaztPcacheMethods);
 162     }
 163   }
 164   pcachetraceOut = out;
 165   return rc;
 166 }
 167
 168 /* Deactivate memory tracing */
 169 int sqlite3PcacheTraceDeactivate(void){
 170   int rc = SQLITE_OK;
 171   if( pcacheBase.xFetch!=0 ){
 172     rc = sqlite3_config(SQLITE_CONFIG_PCACHE2, &pcacheBase);
 173     if( rc==SQLITE_OK ){
 174       memset(&pcacheBase, 0, sizeof(pcacheBase));
 175     }
 176   }
 177   pcachetraceOut = 0;
 178   return rc;
 179 }