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by rbehrends 3398 days ago
> The part where Java really falls down is in memory use & management, which you can see on the binary-tree & mandelbrot benchmarks, where it's roughly 4x slower than C.

binary-tree is not useful for comparing GCed and non-GCed languages. For non-GCed languages, you are allowed to use a memory pool of your choice (the C version uses the Apache Portable Runtime library), for GCed languages you are required to use the standard GC with the default settings (no adjustment of GC parameters permitted). This is apples and oranges.

For mandelbrot, the C version uses handcoded SIMD intrinsics. I.e. it's not even portable to non-x86 processors.
1 comments
flukus 3398 days ago
> For non-GCed languages, you are allowed to use a memory pool of your choice (the C version uses the Apache Portable Runtime library), for GCed languages you are required to use the standard GC with the default settings (no adjustment of GC parameters permitted). This is apples and oranges.

Doesn't that match with how a library would be used in the real world? A c library can create it's own memory pool but a GC one has to live with however it's host is configured.

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rbehrends 3398 days ago
If I were to run a performance-critical application, I'd definitely tune the GC accordingly. It's why the JVM offers several garbage collectors in the first place, for example.

Also, GCed languages aren't prevented from using memory pools, but often they are not part of their common libraries, because there's less need for them.

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flukus 3398 days ago
> If I were to run a performance-critical application, I'd definitely tune the GC accordingly.

But you have to tune it for the performance of the whole application (AFAIK), you can't tune it for an individual algorithm like you can with c. It's a one size fits all approach.

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rbehrends 3398 days ago
1. That goes towards the other point that I made [1] about how microbenchmarks have only limited relevance for the performance of large applications (the performance of memory pools can also change as a result; as an extreme case, multiple large memory pools can lead to swapping).

2. Many GCs allow you to tune performance for individual computations. For example, Erlang allows you to basically start a new lightweight process with a heap large enough so that collection isn't needed and to throw it away at the end; OCaml's GC parameters can be changed while the program is running.

[1] https://news.ycombinator.com/item?id=13747876

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