Add the --fsync flag to kvtest, and document the --nosync flag.

FossilOrigin-Name: 7fdc78a672b2ea6187dcb5fdf32f809bb8e4d501e2434f2233edc3bc2e3acc7c

manifest

@@ -1,5 +1,5 @@
-C Work\stoward\senhancing\skvtest\sto\smeasure\swrite\sperformance.
-D 2017-06-02T19:31:46.986
+C Add\sthe\s--fsync\sflag\sto\skvtest,\sand\sdocument\sthe\s--nosync\sflag.
+D 2017-06-02T23:32:17.964
 F Makefile.in 1cc758ce3374a32425e4d130c2fe7b026b20de5b8843243de75f087c0a2661fb
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 8eeb80162074004e906b53d7340a12a14c471a83743aab975947e95ce061efcc
@@ -925,7 +925,7 @@ F test/json102.test eeb54efa221e50b74a2d6fb9259963b48d7414dca3ce2fdfdeed45cb2848
 F test/json103.test c5f6b85e69de05f6b3195f9f9d5ce9cd179099a0
 F test/json104.test 877d5845f6303899b7889ea5dd1bea99076e3100574d5c536082245c5805dcaa
 F test/keyword1.test 37ef6bba5d2ed5b07ecdd6810571de2956599dff
-F test/kvtest.c 63f9a1c31391f304e87d4854aea54c01afa9e4f6d05e11124598c7415b893a85
+F test/kvtest.c bf2e7ae3de92d98147e8cd49fc550ee3382599aa20b7e2b60038b409a5b2ef34
 F test/lastinsert.test 42e948fd6442f07d60acbd15d33fb86473e0ef63
 F test/laststmtchanges.test ae613f53819206b3222771828d024154d51db200
 F test/like.test 0603f4fa0dad50987f70032c05800cbfa8985302
@@ -1582,7 +1582,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P ab33d299c7dab52703d06f3441c8a98c6c809b2612ec65d71aab2919bd2b1540
-R b213b6f467b3c9502658fd4e2800b6d6
+P fc73e7d2f16386f96c55c42f9830193f7c178521a7ad90c3117b85ef629b5ce4
+R ac814c325af013850c7ab30877776723
 U drh
-Z 24f39ffaffd16b2467372fb4bd435c2b
+Z 8a788cf2631896aff995d8f1a4f42a59

manifest.uuid

@@ -1 +1 @@
-fc73e7d2f16386f96c55c42f9830193f7c178521a7ad90c3117b85ef629b5ce4
+7fdc78a672b2ea6187dcb5fdf32f809bb8e4d501e2434f2233edc3bc2e3acc7c

test/kvtest.c

@@ -90,9 +90,11 @@ static const char zHelp[] =
 "           --cache-size N         Database cache size\n"
 "           --count N              Read N blobs\n"
 "           --desc                 Read blobs in descending order\n"
-"           --integrity-check      Run 'PRAGMA integrity_check' after test\n"
+"           --fsync                Synchronous file writes\n"
+"           --integrity-check      Run \"PRAGMA integrity_check\" after test\n"
 "           --max-id N             Maximum blob key to use\n"
 "           --mmap N               Mmap as much as N bytes of DBFILE\n"
+"           --nosync               Set \"PRAGMA synchronous=OFF\"\n"
 "           --jmode MODE           Set MODE journal mode prior to starting\n"
 "           --random               Read blobs in a random order\n"
 "           --start N              Start reading with this blob key\n"
@@ -541,11 +543,12 @@ static unsigned char *readFile(const char *zName, int *pnByte){
 ** Overwrite a file with randomness.  Do not change the size of the
 ** file.
 */
-static void updateFile(const char *zName, int *pnByte){
+static void updateFile(const char *zName, int *pnByte, int doFsync){
   FILE *out;              /* FILE from which to read content of zName */
   sqlite3_int64 sz;       /* Size of zName in bytes */
   size_t nWritten;        /* Number of bytes actually read */
   unsigned char *pBuf;    /* Content to store on disk */
+  const char *zMode = "wb";   /* Mode for fopen() */
 
   sz = fileSize(zName);
   if( sz<0 ){
@@ -558,11 +561,21 @@ static void updateFile(const char *zName, int *pnByte){
     fatalError("Cannot allocate %lld bytes\n", sz);
   }
   sqlite3_randomness((int)sz, pBuf); 
-  out = fopen(zName, "wb");
+#if defined(_WIN32)
+  if( doFsync ) zMode = "wbc";
+#endif
+  out = fopen(zName, zMode);
   if( out==0 ){
     fatalError("Cannot open \"%s\" for writing\n", zName);
   }
   nWritten = fwrite(pBuf, 1, (size_t)sz, out);
+  if( doFsync ){
+#if defined(_WIN32)
+    fflush(out);
+#else
+    fsync(fileno(out));
+#endif
+  }
   fclose(out);
   if( nWritten!=(size_t)sz ){
     fatalError("Wrote only %d of %d bytes to \"%s\"\n",
@@ -728,6 +741,7 @@ static int runMain(int argc, char **argv){
   int isUpdateTest = 0;       /* Do in-place updates rather than reads */
   int doIntegrityCk = 0;      /* Run PRAGMA integrity_check after the test */
   int noSync = 0;             /* Disable synchronous mode */
+  int doFsync = 0;            /* Update disk files synchronously */
   sqlite3 *db = 0;            /* Database connection */
   sqlite3_stmt *pStmt = 0;    /* Prepared statement for SQL access */
   sqlite3_blob *pBlob = 0;    /* Handle for incremental Blob I/O */
@@ -816,6 +830,10 @@ static int runMain(int argc, char **argv){
       noSync = 1;
       continue;
     }
+    if( strcmp(z, "-fsync")==0 ){
+      doFsync = 1;
+      continue;
+    }
     fatalError("unknown option: \"%s\"", argv[i]);
   }
   if( eType==PATH_DB ){
@@ -884,7 +902,7 @@ static int runMain(int argc, char **argv){
       zKey = sqlite3_mprintf("%s/%06d", zDb, iKey);
       nData = 0;
       if( isUpdateTest ){
-        updateFile(zKey, &nData);
+        updateFile(zKey, &nData, doFsync);
       }else{
         pData = readFile(zKey, &nData);
         sqlite3_free(pData);