--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/dancres/blitz/disk/IOStats.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,88 @@
+package org.dancres.blitz.disk;
+
+import java.util.logging.Level;
+
+class IOStats {
+    private int theAsyncInCount;
+    private int theAsyncOutCount;
+
+    private double theSampleStartTime;
+
+    private double theTimePerOut;
+    private double theTimePerIn;
+
+    private double theInOutLag;
+    private double theInOutRatio;
+
+    private int theQueueSize;
+
+    double getTimePerIn() {
+        return theTimePerIn;
+    }
+
+    double getTimePerOut() {
+        return theTimePerOut;
+    }
+
+    double getInOutRatio() {
+        return theInOutRatio;
+    }
+
+    void incAsyncInCount() {
+        synchronized(this) {
+            ++theAsyncInCount;
+            ++theQueueSize;
+        }
+    }
+
+    int getQueueSize() {
+        synchronized(this) {
+            return theQueueSize;
+        }
+    }
+
+    /**
+       @return <code>true</code> if the io statistics were updated, <code>
+       false</code> otherwise.
+     */
+    boolean incAsyncOutCount() {
+        synchronized(this) {
+            if (theAsyncOutCount == 0)
+                theSampleStartTime = (double) System.currentTimeMillis();
+
+            ++theAsyncOutCount;
+            --theQueueSize;
+
+            /*
+              Probably this should be based on low watermark so the
+              calculation is available before the high watermark is hit.
+              Probably ought to remove desired pending count as well at some
+              point.
+            */
+            if (theAsyncOutCount == 1000) {
+                double myDuration = (double) System.currentTimeMillis() -
+                    theSampleStartTime;
+
+                theTimePerOut = myDuration / 1000.0;
+                theTimePerIn = myDuration / (double) theAsyncInCount;
+
+                theInOutLag = theTimePerOut - theTimePerIn;
+                theInOutRatio = theTimePerOut / theTimePerIn;
+
+                theAsyncOutCount = theAsyncInCount = 0;
+
+                return true;
+            }
+
+            return false;
+        }
+    }
+
+    void dumpStats() {
+        synchronized(this) {
+            WriteDaemon.theLogger.log(Level.INFO, "TPI: " + theTimePerIn +
+                " TPO: " + theTimePerOut + " IOL: " + theInOutLag +
+                " IOR: " + theInOutRatio + " QSZ: " + theQueueSize);
+        }
+    }
+}