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

[Gerard Ziemski]

On Thu, 24 Apr 2025 20:35:39 GMT, Stefan Karlsson <stefank 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.

Ah, you mean like the realloc/malloc refactoring, noted.

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PR Comment: https://git.openjdk.org/jdk/pull/23786#issuecomment-2828835492