Hi Michal, pleased to meet you. I'll be your sponsor. The test will need a legal header, presumably similar to others authored by redhatters.
It is now possible to check in jmh microbenchmarks (but I've never done so myself). The current coding style is non-standard, but deliberate; avoid gratuitous changes like - Node<K,V> e; + Node<K, V> e; As author of concurrent/ConcurrentHashMap/WhiteBox.java ... - I thought you'd need a @modules ... did this test actually pass? - you should have some kind of @summary that includes the word "whitebox" - why not "throws ReflectiveOperationException" ? - your reviewer is a bit on the autistic side, so please change /** to /* on the @test comment (it's not javadoc!) On Tue, Dec 11, 2018 at 11:06 AM Michal Vala <mv...@redhat.com> wrote: > Hi, > > I've been looking into this bug in HashMap where resize() is called > multiple > times when putting whole map into another. > > I come up with following patch: > http://cr.openjdk.java.net/~mvala/jdk/jdk/JDK-8210280/webrev.00/ > > I've tried to do it as little invasive as possible. New resize(int) method > is > called just from putMapEntries for now. Notice that method is called with > size > of the new map. I was experimenting with calling it with 'size()+s', but > this > leads to unwanted space allocation when inserted map rewrites a lot of > existing > keys. > > I've benchmarked this with adding 10millions elements into existing map > and it > gets ~50% improvement: > > unpatched > Benchmark Mode Cnt Score Error Units > MyBenchmark.testMethod thrpt 10 1.248 ± 0.058 ops/s > > patched > Benchmark Mode Cnt Score Error Units > MyBenchmark.testMethod thrpt 10 1.872 ± 0.109 ops/s > > public class MyBenchmark { > static Map<Integer, Integer> mapTocopy = IntStream.range(1, > 10_000_000).boxed().collect(Collectors.toMap(k -> k, > k -> k)); > > @Benchmark > public int testMethod() { > var map = new HashMap<Integer, Integer>(); > map.put(-5, -5); > map.putAll(mapTocopy); > return map.size(); > } > } > > Any ideas for missed corner-cases or some good tests? > > -- > Michal Vala > OpenJDK QE > Red Hat Czech >
