java8 metaspace issue

[Brian Harris]

Yes I should have said OOME instead of 'crash'. Indeed when setting
-XX:MaxMetaspaceSize=20m the program does not throw OOME.

Appears to be a boundary case jvm bug that this will throw OOME when
-XX:MaxMetaspaceSize=10m
after going through the loop 890 times. Otherwise, how else can the OOME be
explained given we're using soft refs?

On Tue, May 5, 2015 at 2:05 AM, Bengt Rutisson <bengt.rutisson at oracle.com>
wrote:

>
> Hi Brian,
>
> On 2015-05-05 05:17, Brian Harris wrote:
>
> Hi,
>
>  I find that this code crashes in 8u40 after getting up to about 900 when
> run with -XX:MaxMetaspaceSize=10m. When run in 7u60 with
> -XX:MaxPermSize=10m it does not crash.
>
>
> Thanks for providing the example program. For me it does not crash but if
> I run with -XX:MaxMetaspaceSize=10m I get an OutOfMemoryError. Does it
> crash for you?
>
> The OutOfMemoryError can be explained by the fact that when you run with
> -XX:MaxPermSize=10m there is some aligning going on and in the end you
> actually end up with a perm gen that is 20m large. Here's what I get when I
> use
>
> $ java -XX:+PrintGCDetails  -XX:MaxPermSize=10m
>
> Heap
>  PSYoungGen      total 150528K, used 10363K [0x0000000758c80000,
> 0x0000000763400000, 0x0000000800000000)
>   eden space 129536K, 8% used
> [0x0000000758c80000,0x000000075969ed58,0x0000000760b00000)
>   from space 20992K, 0% used
> [0x0000000761f80000,0x0000000761f80000,0x0000000763400000)
>   to   space 20992K, 0% used
> [0x0000000760b00000,0x0000000760b00000,0x0000000761f80000)
>  ParOldGen       total 342016K, used 0K [0x000000060a600000,
> 0x000000061f400000, 0x0000000758c80000)
>   object space 342016K, 0% used
> [0x000000060a600000,0x000000060a600000,0x000000061f400000)
>  PSPermGen       total 20480K, used 3382K [0x0000000609200000,
> 0x000000060a600000, 0x000000060a600000)
>   object space 20480K, 16% used
> [0x0000000609200000,0x000000060954dae0,0x000000060a600000)
>
> As you can see the perm gen is 20 m even though I specified 10m on the
> command line.
>
> If I run your program with -XX:MaxMetaspaceSize=20m it passes and does not
> run out of memory.
>
>
> There are no guarantees that you can always just replace MaxPermSize with
> MaxMetaspaceSize. Often it works, but sometimes you have to adjust the
> values. Especially at boundary cases as low as 10m.
>
> Hths,
> Bengt
>
>
>
>  Is that expected? It seems similar to
> https://bugs.openjdk.java.net/browse/JDK-8025635
>
>  Thanks,
> Brian
>
>  // uses Guava's CacheBuilder
>  public class Main {
>
>     public static void main(String[] args) throws Exception {
>         Cache<Integer, Object> cache = CacheBuilder.newBuilder()
>                 .softValues()
>                 .build();
>
>         for (int i = 0; i < 50_000; i++) {
>             URL[] dummyUrls = {new URL("file:" + i + ".jar")};
>             URLClassLoader cl = new URLClassLoader(dummyUrls,
> Thread.currentThread().getContextClassLoader());
>             Object proxy = Proxy.newProxyInstance(cl, new
> Class[]{Foo.class}, new InvocationHandler() {
>                 @Override
>                 public Object invoke(Object proxy, Method method, Object[]
> args) throws Throwable {
>                     return null;
>                 }
>             });
>             cache.put(i, proxy);
>             System.out.println(i);
>         }
>     }
>
>     public interface Foo {
>             void x();
>     }
> }
>
>
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>
>
>
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