[PATCH] Use posix_fallocate instead of ftruncate.

[Sean Silva via llvm-commits]

On Tue, Jul 19, 2016 at 1:06 PM, Rafael Espíndola <
llvm-commits at lists.llvm.org> wrote:

> > Well, is detecting a disk full event so important to risk that it could
> slow
> > down the linker on NFS or such? It'd depend how often you hit it, but to
> me
> > it doesn't feel like a good trade-off.
>
> I would probably say it is. If you are linking on nfs you probably
> cannot expect any reasonable link time right now.
>
> If we want to support that we should resurrect my patch to link to a
> posix_align allocated anonymous memory and then just use write to pass
> it to the os.
>

Yeah, this sounds like the right approach. AFAIK nobody has tested LLD on
NFS and so any behaviors/perf we have there are going to be purely
accidental. Also IIRC mmap on NFS has issues? And we rely on mmap heavily
on the input side too.

-- Sean Silva


>
> In any case, lets benchmark it before we start adding more #ifdefs and
> options.
>
> The attached patch uses a cmake check to avoid making things worse
> (but not any better) on systems that don't have posix_fallocate.
>
> What do you want me to benchmark? Linking the current benchmarks on
> NFS? Is linux as the server OK?
>
> Cheers,
> Rafael
>
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