[PATCH] D71786: RFC: [Support] On Windows, add optional support for rpmalloc

Tue Jan 7 05:23:01 PST 2020

russell.gallop added a comment.

In D71786#1807550 <https://reviews.llvm.org/D71786#1807550>, @maniccoder wrote:

> In D71786#1802970 <https://reviews.llvm.org/D71786#1802970>, @russell.gallop wrote:
>
> > 1). This also seems to improve compile time by around 5% for me. Presumably this is due to some other benefit of rpmalloc as (AFAIK) clang.exe does not use multiple threads.
>
>
> Yes, generally rpmalloc improves single-threaded allocation performance over the default runtime, especially for small block allocations (below 1KiB), enough to warrant using it only for this use case.

Thanks for the info.

>> 2). This can significantly increase memory usage. Part of this can be attributed to the increased parallelism but I don't think that entirely explains it. I think that rpmalloc is using more memory. Have you experimented with settings such as here: https://github.com/mjansson/rpmalloc/blob/develop/CACHE.md?
> 
> I'm looking into some LLVM statistics provided by @aganea to see if the overhead can be reduced without sacrificing too much of the performance gains.

Thanks. In your experience, is rpmalloc performance sensitive to different host machines (i.e. memory hierarchy), or is it mainly dependent on the application (things like allocation sizes)?

> (disclaimer: I'm the author of rpmalloc and will naturally be biased in any discussions regarding its performance)

Okay. Thanks for writing it!

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