RFR: 8317453: NMT: Performance benchmarks are needed to measure speed and memory

[Stefan Karlsson]

On Thu, 24 Apr 2025 20:09:33 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

> > When benchmarking malloc the multi-threaded performance is important. If you take a lock while malloc:ing you probably don't get any significant performance degradation a single-threaded run, but if you malloc from multiple threads you will likely see a significant performance / latency degradation. Has this been considered when thinking about the performance of NMT and this tool?
> 
> I thought about this and I think the appropriate answer is "multithreaded malloc performance" is out of scope of this benchmark. We are not really interested in minute perf characteristics of native calls.
> 
> We are interested in impact of NMT code on the hotspot.

My concern is that if you use this tool to motivate changes to malloc, then the motivation could be incomplete if it doesn't also think about multi-threaded use-cases. Just a heads up for the future.

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PR Comment: https://git.openjdk.org/jdk/pull/23786#issuecomment-2828797549