4 ms·

But reference counting is just a tiny subcomponent of Rust's GC. The majority of Rust's automatic memory management is based on affine types and static code ana

But reference counting is just a tiny subcomponent of Rust's GC. The majority of Rust's automatic memory management is based on affine types and static code analysis, not refcounting. You're just picking subcomponents to make Java solution look better, but what matters for developers is the whole picture. And BTW, I wouldn't be so sure about throughput either. ZGC is capable of allocation rates of the order of only ~5 GB/s, which is way below the theoretical memory bandwidth. I bet jemalloc can do much better.

kaba0 4y ago
The statement was that ZGC (or any JVM GC for that matter) is better than Rust’s GC, which is just naive ref counting. This is true - if we were to create a program that allocates the same amount in both implementations, Java would win by a huge margin.
- pkolaczk 4y ago
  Have you ever tested it by yourself? I tested and no, it didn't win by a huge margin. Malloc+free was only a tad slower than the default Java GC new (stop the world, parallel) but the default GC is much faster than G1 and ZGC so I would not be surprised if malloc could beat those modern ones at allocation rate benchmark.
  - kaba0 4y ago
    Do you have a public benchmark for that? It’s quite hard to write a benchmark that actually measures what we are interested in. Not doubting you, I would be interested only.
    - pkolaczk 4y ago
      This has been on my list of next blog posts for so long. But unfortunately no, not yet.
pron 4y ago
I thought I made it clear in my last comment that I'm not claiming that Java's memory management is somehow "better" than Rust's. I was merely pointing out that even Rust has a GC, and it's not a good one, but it might certainly be good enough for Rust's needs as it doesn't depend on it. Overall, obviously Rust and Java choose very different tradeoffs in their memory management strategy. > ZGC is capable of allocation rates of the order of only ~5 GB/s That was the non-generational ZGC. Indeed, ZGC's max throughput was well below that of ParallelGC and G1. One of the main goals of generational ZGC is to increase the throughput, and as you can see in the video, they got a 4x increase in throughput.

kaba0 4y ago

The statement was that ZGC (or any JVM GC for that matter) is better than Rust’s GC, which is just naive ref counting. This is true - if we were to create a program that allocates the same amount in both implementations, Java would win by a huge margin.

pkolaczk 4y ago
Have you ever tested it by yourself? I tested and no, it didn't win by a huge margin. Malloc+free was only a tad slower than the default Java GC new (stop the world, parallel) but the default GC is much faster than G1 and ZGC so I would not be surprised if malloc could beat those modern ones at allocation rate benchmark.
- kaba0 4y ago
  Do you have a public benchmark for that? It’s quite hard to write a benchmark that actually measures what we are interested in. Not doubting you, I would be interested only.
  - pkolaczk 4y ago
    This has been on my list of next blog posts for so long. But unfortunately no, not yet.

pron 4y ago

I thought I made it clear in my last comment that I'm not claiming that Java's memory management is somehow "better" than Rust's. I was merely pointing out that even Rust has a GC, and it's not a good one, but it might certainly be good enough for Rust's needs as it doesn't depend on it. Overall, obviously Rust and Java choose very different tradeoffs in their memory management strategy. > ZGC is capable of allocation rates of the order of only ~5 GB/s That was the non-generational ZGC. Indeed, ZGC's max throughput was well below that of ParallelGC and G1. One of the main goals of generational ZGC is to increase the throughput, and as you can see in the video, they got a 4x increase in throughput.