From df83fcc4fc5026ce75edd680642f3d46ab5d3507 Mon Sep 17 00:00:00 2001
From: reger <reger18@arcor.de>
Date: Wed, 11 Feb 2015 01:42:01 +0100
Subject: [PATCH] disable optimistic GC assumption in StandardMemoryStrategy
 After several tests found that eom is not prevented. Major reason in testing
 was assumption future GC will free avg of last 5 GC. Disabeling this check
 improved eom exceptions.

Added simplest testcase used for verification
---
 .../kelondro/util/StandardMemoryStrategy.java | 12 +++---
 .../yacy/kelondro/util/MemoryControlTest.java | 43 +++++++++++++++++++
 2 files changed, 49 insertions(+), 6 deletions(-)
 create mode 100644 test/net/yacy/kelondro/util/MemoryControlTest.java

diff --git a/source/net/yacy/kelondro/util/StandardMemoryStrategy.java b/source/net/yacy/kelondro/util/StandardMemoryStrategy.java
index 58d3582d3..35e82732a 100644
--- a/source/net/yacy/kelondro/util/StandardMemoryStrategy.java
+++ b/source/net/yacy/kelondro/util/StandardMemoryStrategy.java
@@ -36,7 +36,7 @@ public class StandardMemoryStrategy extends MemoryStrategy {
 
     private final long[] gcs = new long[5];
     private int gcs_pos = 0;
-    private long properMbyte = 0L;
+    private long properByte = 0L; // treshold
     private long prevTreshold = 0L;
     private int tresholdCount = 0;
     private boolean proper = true;
@@ -157,7 +157,7 @@ public class StandardMemoryStrategy extends MemoryStrategy {
     }
     private boolean request0(final long size, final boolean force) {
     	final long avg = getAverageGCFree();
-    	if (avg >= size) return true;
+    	// if (avg >= size) return true; // optimistic view, GC may just has happened
         long avail = available();
         if (avail >= size) return true;
         if (log.isFine()) {
@@ -177,7 +177,7 @@ public class StandardMemoryStrategy extends MemoryStrategy {
                     + (size >> 10) + " / " + (avail >> 10) + " / " + (avg >> 10) + " KB)");
             }
             checkProper(avail);
-            return avail >= size;
+            return this.proper && avail >= size;
         }
         if (log.isFine()) log.fine("former GCs indicate to not be able to free enough memory (requested/available/average: "
                 + (size >> 10) + " / " + (avail >> 10) + " / " + (avg >> 10) + " KB)");
@@ -209,13 +209,13 @@ public class StandardMemoryStrategy extends MemoryStrategy {
      */
     @Override
     protected void setProperMbyte(final long mbyte) {
-    	this.properMbyte = mbyte;
+    	this.properByte = mbyte << 20; // convert to byte
     	this.tresholdCount = 0;
     }
 
     private void checkProper(final long available) {
     	// disable proper state if memory is less than treshold - 4 times, maximum 11 minutes between each detection
-    	if ((available >> 20) < this.properMbyte) {
+    	if ((available) < this.properByte) {
     		final long t = System.currentTimeMillis();
     		if(this.prevTreshold + 11L /* minutes */ * 60000L > t) {
     			this.tresholdCount++;
@@ -227,7 +227,7 @@ public class StandardMemoryStrategy extends MemoryStrategy {
 
 			log.info("checkProper: below treshold; tresholdCount: " + this.tresholdCount + "; proper: " + this.proper);
     	}
-    	else if (!this.proper && (available >> 20) > (this.properMbyte * 2L)) // we were wrong!
+    	else if (!this.proper && (available) > (this.properByte * 2L)) // we were wrong!
     		resetProperState();
     }
 
diff --git a/test/net/yacy/kelondro/util/MemoryControlTest.java b/test/net/yacy/kelondro/util/MemoryControlTest.java
new file mode 100644
index 000000000..5c8666436
--- /dev/null
+++ b/test/net/yacy/kelondro/util/MemoryControlTest.java
@@ -0,0 +1,43 @@
+
+package net.yacy.kelondro.util;
+
+import static org.junit.Assert.assertTrue;
+import org.junit.Test;
+
+
+public class MemoryControlTest {
+
+    final int onemb = 1024 * 1024;
+
+    /**
+     * Test of request method, of class MemoryControl.
+     */
+    @Test
+    public void testRequest_StandardStrategy() {
+        MemoryControl.setStandardStrategy(true);
+        MemoryControl.setProperMbyte(24);
+
+        int memblock = onemb * 13; // memsize to allocate
+
+        int iterations = (int) MemoryControl.available() / memblock;
+        int arraysize = (int) MemoryControl.maxMemory() / memblock + 10;
+
+        byte[][] x = new byte[arraysize][];
+
+        int i = 0;
+        
+        while (i < arraysize && MemoryControl.request(memblock, false)) {
+            x[i] = new byte[memblock];
+            // for realistic test produce some memory avail to GC
+            if (MemoryControl.request(memblock, false)) {
+                x[i] = new byte[memblock];
+            }
+        
+            i++;
+        }
+        System.out.println("allocated " + i + " * " + memblock/onemb + " MB = " + i*memblock/onemb + " MB");
+
+        assertTrue(i >= iterations);
+    }
+
+}