[llvm-dev] Benchmark LNT weird thread behaviour

Renato Golin via llvm-dev llvm-dev at lists.llvm.org
Tue Sep 20 04:29:48 PDT 2016

On 20 September 2016 at 01:17, Chris Matthews <chris.matthews at apple.com> wrote:
> There seems to be three interesting flags in your LNT invocations:
>  -j2 --threads=1 --build-threads=4
> Since -j and --threads are the same flag, I think that is the problem.  The
> first -j flag is at the start of the LNT command, perhaps that is coming
> from a different part of zorg?

-j2 is from "jobs=2" in the builder's argument list, to compile Clang.
This also gets passed to LNT, since nt_flags is not required, and you
do want to use all cores if nothing is specified.

Of course, when --threads is specified, you have the conflict, but
since this argument is not required, I wouldn't want to omit the -j2
from LNT at all.

I could "fix" this in our builder to not pass -jN into LNT and always
use nt_flags, but I don't think that is a good fix, since other users
will have odd behaviour on their side. Unless that's the kind of
behaviour we *want* to encode, of course.

What do you think?


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