franz1981 commented on a change in pull request #2645: ARTEMIS-2321 Paging
scalability and GC improvement
URL: https://github.com/apache/activemq-artemis/pull/2645#discussion_r279261506
##########
File path:
artemis-core-client/src/main/java/org/apache/activemq/artemis/utils/SoftValueLongObjectHashMap.java
##########
@@ -21,26 +21,26 @@
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
-import java.util.HashMap;
-import java.util.HashSet;
+import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;
-import java.util.concurrent.atomic.AtomicLong;
+import io.netty.util.collection.LongObjectHashMap;
+import io.netty.util.collection.LongObjectMap;
import org.jboss.logging.Logger;
-public class SoftValueHashMap<K, V extends SoftValueHashMap.ValueCache>
implements Map<K, V> {
+public class SoftValueLongObjectHashMap<V extends
SoftValueLongObjectHashMap.ValueCache> implements LongObjectMap<V> {
- private static final Logger logger =
Logger.getLogger(SoftValueHashMap.class);
+ private static final Logger logger =
Logger.getLogger(SoftValueLongObjectHashMap.class);
// The soft references that are already good.
// too bad there's no way to override the queue method on ReferenceQueue,
so I wouldn't need this
private final ReferenceQueue<V> refQueue = new ReferenceQueue<>();
- private final Map<K, AggregatedSoftReference> mapDelegate = new HashMap<>();
+ private final LongObjectMap<AggregatedSoftReference<V>> mapDelegate = new
LongObjectHashMap<>();
Review comment:
But I wanted to avoid the boxing/unboxing cost: the page cache (that uses
this soft value map) is sensible to GC cycles and the more is your allocation
rate, the more likely you will have a minor GC, making the cache to clean some
of its entries...
Avoiding boxing/unboxing is just a way to let the entries stays much longer
and makes this map more effective.
TBH I don't know (the details I mean) why we are using a soft value map
here: I would have used a LRU map instead with a fixed size of entries instead
like
https://github.com/real-logic/agrona/blob/master/agrona/src/main/java/org/agrona/collections/IntLruCache.java
: need to ask @clebertsuconic about it...
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