nicer latency test admin command

2 files changed, 24 insertions, 15 deletions

diff --git a/db/dbcommands_admin.cpp b/db/dbcommands_admin.cpp
index 6a8bbed9db1..ad77c66ce59 100644
--- a/db/dbcommands_admin.cpp
+++ b/db/dbcommands_admin.cpp
@@ -91,7 +91,8 @@ namespace mongo {
             }
             catch(...) { }
 
-            {
+            BSONObjBuilder bb[2];
+            for( int pass = 0; pass < 2; pass++ ) {
                 LogFile f(p.string());
                 AlignedBuilder b(1024 * 1024);
                 {
@@ -99,7 +100,7 @@ namespace mongo {
                     for( int i = 0 ; i < 100; i++ ) { 
                         f.synchronousAppend(b.buf(), 8192);
                     }
-                    result.append("timeMillis8KB", t.millis() / 100.0);
+                    bb[pass].append("8KB", t.millis() / 100.0);
                 }
                 {
                     const int N = 50;
@@ -113,16 +114,19 @@ namespace mongo {
                     }
                     long long y = t2.micros() - 4*N*1000;
                     // not really trusting the timer granularity on all platforms so whichever is higher of x and y
-                    result.append("timeMillis8KBWithPauses", max(x,y) / (N*1000.0));
+                    bb[pass].append("8KBWithPauses", max(x,y) / (N*1000.0));
                 }
                 {
                     Timer t;
                     for( int i = 0 ; i < 20; i++ ) { 
                         f.synchronousAppend(b.buf(), 1024 * 1024);
                     }
-                    result.append("timeMillis1MB", t.millis() / 20.0);
+                    bb[pass].append("1MB", t.millis() / 20.0);
                 }
+                // second time around, we are prealloced.
             }
+            result.append("timeMillis", bb[0].obj());
+            result.append("timeMillisWithPrealloc", bb[1].obj());
 
             try { 
                 remove(p);
@@ -131,7 +135,6 @@ namespace mongo {
 
             return 1;
         }
-
     } journalLatencyTestCmd;
 
     class ValidateCmd : public Command {
diff --git a/db/dur_journal.cpp b/db/dur_journal.cpp
index b625ecb45b4..404a2691ff7 100644
--- a/db/dur_journal.cpp
+++ b/db/dur_journal.cpp
@@ -183,18 +183,25 @@ namespace mongo {
         void journalCleanup() { j.cleanup(); }
 
         // throws
+        void preallocateFile(filesystem::path p, unsigned long long len) {
+            if( exists(p) ) 
+                return;
+
+            const unsigned BLKSZ = 1024 * 1024;
+            log() << "preallocating a journal file " << p.string() << endl;
+            LogFile f(p.string());
+            AlignedBuilder b(BLKSZ);
+            for( unsigned long long x = 0; x < len; x += BLKSZ ) { 
+                f.synchronousAppend(b.buf(), BLKSZ);
+            }
+        }
+
+        // throws
         void _preallocateFiles() {
             for( int i = 0; i <= 2; i++ ) {
                 string fn = str::stream() << "prealloc." << i;
                 filesystem::path filepath = getJournalDir() / fn;
 
-                if( exists(filepath) ) 
-                    continue;
-
-                const unsigned BLKSZ = 1024 * 1024;
-                log() << "preallocating a journal file " << filepath.string() << endl;
-                LogFile f(filepath.string());
-                AlignedBuilder b(BLKSZ);
                 unsigned long long limit = Journal::DataLimit;
                 if( debug && i == 1 ) { 
                     // moving 32->64, the prealloc files would be short.  that is "ok", but we want to exercise that 
@@ -203,11 +210,10 @@ namespace mongo {
                     // work anyway.
                     limit = 16 * 1024 * 1024;
                 }
-                for( unsigned long long x = 0; x < limit; x += BLKSZ ) { 
-                    f.synchronousAppend(b.buf(), BLKSZ);
-                }
+                preallocateFile(filepath, limit);
             }
         }
+
         void preallocateFiles() {
             try {
                 _preallocateFiles();