More efficient implementation of a lookaside allocator that supports mini (in this case, harcoded to 128B) slots.

FossilOrigin-Name: b02fdc09c838f355d9efce57f817d6a86153153b4a1f2b763914f4aaa34cb76e

manifest

@@ -1,5 +1,5 @@
-C Fix\sgoofy\sstring\sformatting\sin\slemon.c\sthat\sdates\sfrom\sthe\sK&R-C\sdays.
+C More\sefficient\simplementation\sof\sa\slookaside\sallocator\sthat\ssupports\smini\s(in\sthis\scase,\sharcoded\sto\s128B)\sslots.
-D 2019-12-12T00:20:40.700
+D 2019-12-12T02:50:07.468
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -491,8 +491,8 @@ F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
 F src/insert.c 5de3fd62bd1a692353c8f9c7bbde658f0b579f195620ca3cde1948a53015dddd
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c d74f5e7bd51f3c9d283442473eb65aef359664efd6513591c03f01881c4ae2da
-F src/main.c 868ae7db7a54fe859bf2ca8b7a4f24e9fa03a6134abfb7c9801d08411ef5dacb
+F src/main.c dc4fe09174ef0c11204ca90ed46323471c127c9d18266ec97ee1bca871200e99
-F src/malloc.c 550021fcae36f0ffe9f8563d83e6385f9df307a854d55d7d0abb7241ee8dbcc6
+F src/malloc.c 350d345ab12aa089f3dbd30b4db9b57e486c9dd920d275d1775aa5b6899199ff
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c c12a42539b1ba105e3707d0e628ad70e611040d8f5e38cf942cee30c867083de
 F src/mem2.c f1940d9e91948dd6a908fbb9ce3835c36b5d83c3
@@ -532,9 +532,9 @@ F src/shell.c.in 4a3a9e1c11847b1904f2b01d087af1c052f660902755abab457cab1756817de
 F src/sqlite.h.in 2a23e8161775253d9cf383c2c6aa559005dc787d350dcb0be67a6c4cc3bd1d19
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 72af51aa4e912e14cd495fb6e7fac65f0940db80ed950d90911aff292cc47ce2
-F src/sqliteInt.h 1ac4dfde728b9d5812d1223d668d5e1f43c6fe4f469d6a7a482f298a10a03210
+F src/sqliteInt.h 7965727cc420b5e9ab79f4ba8bda8e806ba315c6e9f489e83f0202f3397fb522
 F src/sqliteLimit.h 1513bfb7b20378aa0041e7022d04acb73525de35b80b252f1b83fedb4de6a76b
-F src/status.c 46e7aec11f79dad50965a5ca5fa9de009f7d6bde08be2156f1538a0a296d4d0e
+F src/status.c 0fe55b92810509eac821ded2e177e1da944a78cdcdfec7813ad1d6b36d6d667e
 F src/table.c b46ad567748f24a326d9de40e5b9659f96ffff34
 F src/tclsqlite.c 8cd2600e8de23dff6cdf84d39f46ca57139b061b28f6f80b166bace17d52ab1c
 F src/test1.c c654981c1d86ebc90dd23fcc0969e6c85e28112f0acc2e2224a97a2a33e7c42f
@@ -1852,7 +1852,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 4d6d2fc046d586a1e5989bbb2757f13d0371fbfad0acf45a0e2fd77dffd8d8f9
+P 48ba5e5a2227257cebafacbb09e9dd91d9b89ab2d52a8b4e4113c1d017d95f41
-R 5e026b3cfa5e818c2e50f705eaa7c6b6
+R 7ee7a134ba45ae790f475dbb2e983799
-U drh
+T *branch * mini-lookaside-take-2
-Z d2668f11b5269bc264b434444e0b4796
+T *sym-mini-lookaside-take-2 *
+T -sym-trunk *
+U numist
+Z aef044ee81b705b7df5a6b1d29e511a6

manifest.uuid

@@ -1 +1 @@
-48ba5e5a2227257cebafacbb09e9dd91d9b89ab2d52a8b4e4113c1d017d95f41
+b02fdc09c838f355d9efce57f817d6a86153153b4a1f2b763914f4aaa34cb76e

src/main.c

@@ -683,6 +683,7 @@ int sqlite3_config(int op, ...){
 static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
 #ifndef SQLITE_OMIT_LOOKASIDE
   void *pStart;
+  sqlite3_int64 szAlloc = sz*(sqlite3_int64)cnt;
   
   if( sqlite3LookasideUsed(db,0)>0 ){
     return SQLITE_BUSY;
@@ -705,7 +706,7 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
     pStart = 0;
   }else if( pBuf==0 ){
     sqlite3BeginBenignMalloc();
-    pStart = sqlite3Malloc( sz*(sqlite3_int64)cnt );  /* IMP: R-61949-35727 */
+    pStart = sqlite3Malloc( szAlloc );  /* IMP: R-61949-35727 */
     sqlite3EndBenignMalloc();
     if( pStart ) cnt = sqlite3MallocSize(pStart)/sz;
   }else{
@@ -714,6 +715,15 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
   db->lookaside.pStart = pStart;
   db->lookaside.pInit = 0;
   db->lookaside.pFree = 0;
+#ifndef SQLITE_OMIT_MINI_LOOKASIDE
+  db->lookaside.pMiniInit = 0;
+  db->lookaside.pMiniFree = 0;
+  /* The arithmetic below causes the number of large lookaside slots to be 1/3
+  ** the number of mini slots, based on the observation that 75% of allocations
+  ** are <=128B.
+  */
+  cnt = szAlloc/(3*128+sz);
+#endif
   db->lookaside.sz = (u16)sz;
   db->lookaside.szTrue = (u16)sz;
   if( pStart ){
@@ -727,6 +737,16 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
       db->lookaside.pInit = p;
       p = (LookasideSlot*)&((u8*)p)[sz];
     }
+#ifndef SQLITE_OMIT_MINI_LOOKASIDE
+    db->lookaside.pMiddle = p;
+    /* Fill the remainder of the buffer with mini slots */
+    while(p<=(LookasideSlot*)&((u8*)pStart)[szAlloc-128]){
+      p->pNext = db->lookaside.pMiniInit;
+      db->lookaside.pMiniInit = p;
+      db->lookaside.nSlot++;
+      p = (LookasideSlot*)&((u8*)p)[128];
+    }
+#endif
     db->lookaside.pEnd = p;
     db->lookaside.bDisable = 0;
     db->lookaside.bMalloced = pBuf==0 ?1:0;

src/malloc.c

@@ -332,6 +332,13 @@ int sqlite3MallocSize(void *p){
   assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
   return sqlite3GlobalConfig.m.xSize(p);
 }
+static int lookasideMallocSize(sqlite3 *db, void *p){
+#ifndef SQLITE_OMIT_MINI_LOOKASIDE    
+  return p<db->lookaside.pMiddle ? db->lookaside.szTrue : 128;
+#else
+  return db->lookaside.szTrue;
+#endif  
+}
 int sqlite3DbMallocSize(sqlite3 *db, void *p){
   assert( p!=0 );
   if( db==0 || !isLookaside(db,p) ){
@@ -347,7 +354,7 @@ int sqlite3DbMallocSize(sqlite3 *db, void *p){
     return sqlite3GlobalConfig.m.xSize(p);
   }else{
     assert( sqlite3_mutex_held(db->mutex) );
-    return db->lookaside.szTrue;
+    return lookasideMallocSize(db, p);
   }
 }
 sqlite3_uint64 sqlite3_msize(void *p){
@@ -397,6 +404,17 @@ void sqlite3DbFreeNN(sqlite3 *db, void *p){
     }
     if( isLookaside(db, p) ){
       LookasideSlot *pBuf = (LookasideSlot*)p;
+#ifndef SQLITE_OMIT_MINI_LOOKASIDE
+      if( p>=db->lookaside.pMiddle ){
+# ifdef SQLITE_DEBUG
+        /* Trash all content in the buffer being freed */
+        memset(p, 0xaa, 128);
+# endif
+        pBuf->pNext = db->lookaside.pMiniFree;
+        db->lookaside.pMiniFree = pBuf;
+        return;
+      }
+#endif
 #ifdef SQLITE_DEBUG
       /* Trash all content in the buffer being freed */
       memset(p, 0xaa, db->lookaside.szTrue);
@@ -564,6 +582,18 @@ void *sqlite3DbMallocRawNN(sqlite3 *db, u64 n){
       return db->mallocFailed ? 0 : dbMallocRawFinish(db, n);
     }
     db->lookaside.anStat[1]++;
+# ifndef SQLITE_OMIT_MINI_LOOKASIDE
+  }else if( n<=128 ){
+    if( (pBuf = db->lookaside.pMiniFree)!=0 ){
+      db->lookaside.pMiniFree = pBuf->pNext;
+      db->lookaside.anStat[0]++;
+      return (void*)pBuf;
+    }else if( (pBuf = db->lookaside.pMiniInit)!=0 ){
+      db->lookaside.pMiniInit = pBuf->pNext;
+      db->lookaside.anStat[0]++;
+      return (void*)pBuf;
+    }
+# endif
   }else if( (pBuf = db->lookaside.pFree)!=0 ){
     db->lookaside.pFree = pBuf->pNext;
     db->lookaside.anStat[0]++;
@@ -597,7 +627,7 @@ void *sqlite3DbRealloc(sqlite3 *db, void *p, u64 n){
   assert( db!=0 );
   if( p==0 ) return sqlite3DbMallocRawNN(db, n);
   assert( sqlite3_mutex_held(db->mutex) );
-  if( isLookaside(db,p) && n<=db->lookaside.szTrue ) return p;
+  if( isLookaside(db,p) && n<lookasideMallocSize(db, p) ) return p;
   return dbReallocFinish(db, p, n);
 }
 static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n){
@@ -608,7 +638,7 @@ static SQLITE_NOINLINE void *dbReallocFinish(sqlite3 *db, void *p, u64 n){
     if( isLookaside(db, p) ){
       pNew = sqlite3DbMallocRawNN(db, n);
       if( pNew ){
-        memcpy(pNew, p, db->lookaside.szTrue);
+        memcpy(pNew, p, lookasideMallocSize(db, p));
         sqlite3DbFree(db, p);
       }
     }else{

src/sqliteInt.h

@@ -1287,6 +1287,11 @@ struct Lookaside {
   u32 anStat[3];          /* 0: hits.  1: size misses.  2: full misses */
   LookasideSlot *pInit;   /* List of buffers not previously used */
   LookasideSlot *pFree;   /* List of available buffers */
+#ifndef SQLITE_OMIT_MINI_LOOKASIDE
+  LookasideSlot *pMiniInit; /* List of mini buffers not prediously used */
+  LookasideSlot *pMiniFree; /* List of available mini buffers */
+  void *pMiddle;          /* An address between the fullsize and mini buffers */
+#endif
   void *pStart;           /* First byte of available memory space */
   void *pEnd;             /* First byte past end of available space */
 };

src/status.c

@@ -188,6 +188,10 @@ static u32 countLookasideSlots(LookasideSlot *p){
 int sqlite3LookasideUsed(sqlite3 *db, int *pHighwater){
   u32 nInit = countLookasideSlots(db->lookaside.pInit);
   u32 nFree = countLookasideSlots(db->lookaside.pFree);
+#ifndef SQLITE_OMIT_MINI_LOOKASIDE
+  nInit += countLookasideSlots(db->lookaside.pMiniInit);
+  nFree += countLookasideSlots(db->lookaside.pMiniFree);
+#endif
   if( pHighwater ) *pHighwater = db->lookaside.nSlot - nInit;
   return db->lookaside.nSlot - (nInit+nFree);
 }
@@ -220,6 +224,15 @@ int sqlite3_db_status(
           db->lookaside.pInit = db->lookaside.pFree;
           db->lookaside.pFree = 0;
         }
+#ifndef SQLITE_OMIT_MINI_LOOKASIDE
+        p = db->lookaside.pMiniFree;
+        if( p ){
+          while( p->pNext ) p = p->pNext;
+          p->pNext = db->lookaside.pMiniInit;
+          db->lookaside.pMiniInit = db->lookaside.pMiniFree;
+          db->lookaside.pMiniFree = 0;
+        }
+#endif
       }
       break;
     }