RFR: 8261154: Memory leak in Java_java_lang_ClassLoader_defineClass0 with long class names

[Thomas Stuefe]

On Thu, 4 Feb 2021 14:23:56 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> This patch resolves a potential memory leak in Java_java_lang_ClassLoader_defineClass0
> 
> I've not figured a good way to write a regression test. A crude way to manually verify the leak and the fix is provided by the added microbenchmark that triggers the malloc in ClassLoader.c and the associated leak.
> 
> E.g., running this with `/usr/bin/time -v $BUILD_DIR/images/jdk/bin/java -Xmx256m -jar $BUILD_DIR/images/test/micro/benchmarks.jar LookupDef.*WeakClass.loadLong -f 0 -i  N | grep "Maximum resident set"` yields:
> 
> Baseline:
> N = 20     Maximum resident set size (kbytes): 544860
> N = 50     Maximum resident set size (kbytes): 818532
> N = 100    Maximum resident set size (kbytes): 1388560
> Patch:
> N = 20     Maximum resident set size (kbytes): 480476
> N = 50     Maximum resident set size (kbytes): 764040
> N = 100    Maximum resident set size (kbytes): 782920

Hi Cleas,

looks good but why changing the the NULL comparisons? 

If you wanted to simplify you could completely omit the NULL checks since free(NULL) is a noop. And potentially merge the labels - where there are two - into one.

Cheers, Thomas

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PR: https://git.openjdk.java.net/jdk/pull/2407