Add additional DBSTATUS options for measuring the hit and miss rates against
the lookaside memory pool - information useful in tuning the lookaside size.
Currently experimental pending analysis of performance impact.
FossilOrigin-Name: 34613f1dc54c638531ca2f5907b71fbe8841233e
diff --git a/src/malloc.c b/src/malloc.c
index 2c78979..a3a9e0f 100644
--- a/src/malloc.c
+++ b/src/malloc.c
@@ -616,14 +616,20 @@
if( db->mallocFailed ){
return 0;
}
- if( db->lookaside.bEnabled && n<=db->lookaside.sz
- && (pBuf = db->lookaside.pFree)!=0 ){
- db->lookaside.pFree = pBuf->pNext;
- db->lookaside.nOut++;
- if( db->lookaside.nOut>db->lookaside.mxOut ){
- db->lookaside.mxOut = db->lookaside.nOut;
+ if( db->lookaside.bEnabled ){
+ if( n>db->lookaside.sz ){
+ db->lookaside.anStat[1]++;
+ }else if( (pBuf = db->lookaside.pFree)==0 ){
+ db->lookaside.anStat[2]++;
+ }else{
+ db->lookaside.pFree = pBuf->pNext;
+ db->lookaside.nOut++;
+ db->lookaside.anStat[0]++;
+ if( db->lookaside.nOut>db->lookaside.mxOut ){
+ db->lookaside.mxOut = db->lookaside.nOut;
+ }
+ return (void*)pBuf;
}
- return (void*)pBuf;
}
}
#else
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index 84999d4..226c5f9 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -5509,6 +5509,28 @@
** <dd>This parameter returns the number of lookaside memory slots currently
** checked out.</dd>)^
**
+** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_HIT</dt>
+** <dd>This parameter returns the number malloc attempts that were
+** satisfied using lookaside memory. Only the high-water value is meaningful;
+** the current value is always zero.
+** checked out.</dd>)^
+**
+** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE</dt>
+** <dd>This parameter returns the number malloc attempts that might have
+** been satisfied using lookaside memory but failed due to the amount of
+** memory requested being larger than the lookaside slot size.
+** Only the high-water value is meaningful;
+** the current value is always zero.
+** checked out.</dd>)^
+**
+** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL</dt>
+** <dd>This parameter returns the number malloc attempts that might have
+** been satisfied using lookaside memory but failed due to all lookaside
+** memory already being in use.
+** Only the high-water value is meaningful;
+** the current value is always zero.
+** checked out.</dd>)^
+**
** ^(<dt>SQLITE_DBSTATUS_CACHE_USED</dt>
** <dd>This parameter returns the approximate number of of bytes of heap
** memory used by all pager caches associated with the database connection.)^
@@ -5531,11 +5553,14 @@
** </dd>
** </dl>
*/
-#define SQLITE_DBSTATUS_LOOKASIDE_USED 0
-#define SQLITE_DBSTATUS_CACHE_USED 1
-#define SQLITE_DBSTATUS_SCHEMA_USED 2
-#define SQLITE_DBSTATUS_STMT_USED 3
-#define SQLITE_DBSTATUS_MAX 3 /* Largest defined DBSTATUS */
+#define SQLITE_DBSTATUS_LOOKASIDE_USED 0
+#define SQLITE_DBSTATUS_CACHE_USED 1
+#define SQLITE_DBSTATUS_SCHEMA_USED 2
+#define SQLITE_DBSTATUS_STMT_USED 3
+#define SQLITE_DBSTATUS_LOOKASIDE_HIT 4
+#define SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE 5
+#define SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL 6
+#define SQLITE_DBSTATUS_MAX 6 /* Largest defined DBSTATUS */
/*
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 4f0e08e..5233e99 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -737,6 +737,7 @@
u8 bMalloced; /* True if pStart obtained from sqlite3_malloc() */
int nOut; /* Number of buffers currently checked out */
int mxOut; /* Highwater mark for nOut */
+ int anStat[3]; /* 0: hits. 1: size misses. 2: full misses */
LookasideSlot *pFree; /* List of available buffers */
void *pStart; /* First byte of available memory space */
void *pEnd; /* First byte past end of available space */
diff --git a/src/status.c b/src/status.c
index 7f05f1c..96759fd 100644
--- a/src/status.c
+++ b/src/status.c
@@ -116,6 +116,22 @@
break;
}
+ case SQLITE_DBSTATUS_LOOKASIDE_HIT:
+ case SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE:
+ case SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL: {
+ testcase( op==SQLITE_DBSTATUS_LOOKASIDE_HIT );
+ testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE );
+ testcase( op==SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL );
+ assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)>=0 );
+ assert( (op-SQLITE_DBSTATUS_LOOKASIDE_HIT)<3 );
+ *pCurrent = 0;
+ *pHighwater = db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT];
+ if( resetFlag ){
+ db->lookaside.anStat[op - SQLITE_DBSTATUS_LOOKASIDE_HIT] = 0;
+ }
+ break;
+ }
+
/*
** Return an approximation for the amount of memory currently used
** by all pagers associated with the given database connection. The