Re: JIT compiling with LLVM v11

Hi,

On 2018-03-15 17:19:23 +0100, Catalin Iacob wrote:
> On Thu, Mar 15, 2018 at 1:20 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > I don't really live in the RHEL world, but I wonder if
> > https://developers.redhat.com/blog/2017/10/04/red-hat-adds-go-clangllvm-rust-compiler-toolsets-updates-gcc/
> > is relevant?
>
> Indeed. It might be a bit awkward for packagers to depend on something
> from Software Collections, for example because they come as separate
> trees in /opt that are by default not in your path or dynamic loader
> path - one needs to run everything via a scl wrapper or source the
> /opt/rh/llvm-toolset-7/enable file to get the appropriate PATH and
> LD_LIBRARY_PATH settings, But it seems doable.

It'd be just for clang, and they're not *forced* to do it, it's an
optional dependency. So I think I'm ok with that.

> I just installed llvm-toolset-7 (the LLVM version is 4.0.1) on RHEL
> 7.4 and did a build of your tree at
> 475b4da439ae397345ab3df509e0e8eb26a8ff39. make installcheck passes for
> both the default config and a server forced to jit everything (I
> think) via:
> jit_above_cost = '0'
> jit_inline_above_cost = '0'
> jit_optimize_above_cost = '0'
>
> As a side note, this increases the runtime from approx 4 min to 18
> min.

Sure, that jits everything, which is obviously pointless to do for
performancereasons. Especially SQL functions play very badly, because
they're replanned every execution. But it's good for testing ;)

> Disabling jit completely with -1 in all of the above yields 3 min
> 48s, close to the default question raising maybe the question of how
> much coverage does jit get with the default config.

A bit, but not hugely so. I'm not too concerned about that. I plan to
stand up a few buildfarm animals testing JITing with everything on w/
various LLVM versions.

> The build was with the newer gcc 7.2.1 from the aforementioned
> collections, I'll try the system gcc as well. I run a buildfarm animal
> (katydid) on this RHEL. When JIT gets committed I'll make it use
> --with-llvm against this Software Collections LLVM.

Cool! Thanks for testing!

Greetings,

Andres Freund