[RFC] Using large pages for large hash tables

[Rui Ueyama via llvm-commits]

On Mon, Oct 17, 2016 at 8:38 AM, Rafael Espíndola <
rafael.espindola at gmail.com> wrote:

> I did a quick and dirty experiment to use large pages when a hash
> table gets big. The results for lld are pretty impressive (see
> attached file, but basically 1.04X faster link of files with debug
> info).
>
> I tested disabling madvise and the performance goes back to what it
> was, so it is really the large pages that improves the performance.
>
> The main question is then what the interface should look like. On
> linux the abstraction could be
>
> std::pair<void *, size_t> mallocLarge(size_t Size);
>
> which return the allocated memory and how much was actually allocated.
> The pointer can be passed to free once it is no longer needed.
>

I wonder why you want to return a size instead of just a void pointer.


>
> The fallback implementation just calls malloc and returns Size unmodified.
>
> On linux x86_64 if size is larger than 2MiB we use posix_memalign and
> madvise.
>
> Would the same interface work on windows?
>
> Cheers,
> Rafael
>
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