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From ahgittin <...@git.apache.org>
Subject [GitHub] brooklyn-server pull request #331: Fix some memory leaks and better memory u...
Date Mon, 26 Sep 2016 09:40:37 GMT
Github user ahgittin commented on a diff in the pull request:

    https://github.com/apache/brooklyn-server/pull/331#discussion_r80439204
  
    --- Diff: utils/common/src/main/java/org/apache/brooklyn/util/javalang/MemoryUsageTracker.java
---
    @@ -68,5 +87,76 @@ public long getBytesUsed() {
             memoryTrackedReferences.cleanUp();
             return bytesUsed.get();
         }
    +
    +    /** forces all soft references to be cleared by trying to allocate an enormous chunk
of memory,
    +     * returns a description of what was done 
    +     * (tune with with {@link #forceClearSoftReferences(long, int)} 
    +     * for greater than 200M precision in the output message, if you really care about
that) */
    +    public static String forceClearSoftReferences() {
    +        return forceClearSoftReferences(1000*1000, Integer.MAX_VALUE);
    +    }
    +    /** as {@link #forceClearSoftReferences()} but gives control over headroom and max
chunk size.
    +     * it tries to undershoot by headroom as it approaches maximum (and then overshoot)
    +     * to minimize the chance we take exactly all the memory and starve another thread;
    +     * and it uses the given max chunk size in cases where the caller wants more precision
    +     * (the available memory will be fragmented so the smaller the chunks the more it
can
    +     * fill in, but at the expense of time and actual memory provisioned) */
    +    public static String forceClearSoftReferences(long headroom, int maxChunk) {
    +        final long HEADROOM = 1000*1000;  
    +        long lastAmount = 0;
    +        long nextAmount = 0;
    +        long oldUsed = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
    +        try {
    +            List<byte[]> dd = MutableList.of();
    +            while (true) {
    +                int size = (int)Math.min(Runtime.getRuntime().freeMemory()-HEADROOM,
maxChunk);
    +                if (size<HEADROOM) {
    +                    // do this to minimize the chance another thread gets an OOME
    +                    // due to us leaving just a tiny amount of memory 
    +                    size = (int) Math.min(size + 2*HEADROOM, maxChunk);
    +                }
    +                nextAmount += size;
    +                dd.add(new byte[size]);
    +                lastAmount = nextAmount;
    +            }
    +        } catch (OutOfMemoryError e) { /* expected */ }
    +        System.gc(); System.gc();
    +        long newUsed = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
    +        return "allocated " + Strings.makeSizeString((lastAmount+nextAmount)/2) +
    +                (lastAmount<nextAmount ? " +- "+Strings.makeSizeString((nextAmount-lastAmount)/2)
: "")
    +                +" really free memory in "+Strings.makeSizeString(maxChunk)+" chunks;
"
    +                +"memory used from "+Strings.makeSizeString(oldUsed)+" -> "+Strings.makeSizeString(newUsed)+"
/ "+
    +                    Strings.makeSizeString(Runtime.getRuntime().totalMemory());
    +    }
         
    +    /** Tracking for soft usage through SoftlyPresent instances */
    +    public static class SoftUsageTracker {
    +        private Cache<Object,SoftReference<?>> cache = null;
    +        public synchronized void enable() {
    +            cache = CacheBuilder.newBuilder().weakKeys().build();
    +        }
    +        public synchronized void disable() {
    +            cache = null;
    +        }
    +        public long getTotalEntries() {
    +            return cache.size();
    --- End diff --
    
    yes


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