Re: JIT compiling with LLVM v9.0

From: Andres Freund <andres(at)anarazel(dot)de>
To: Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: JIT compiling with LLVM v9.0
Date: 2018-01-26 08:23:41
Message-ID: 20180126082340.cy42v56rwuboe5wv@alap3.anarazel.de
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Hi,

Thanks for testing things out!

On 2018-01-26 10:44:24 +0300, Konstantin Knizhnik wrote:
> Also I noticed that parallel execution didsables JIT.

Oh, oops, I broke that recently by moving where the decisition about
whether to jit or not is. There actually is JITing, but only in the
leader.

> Are there any principle problems with combining JIT and parallel execution?

No, there's not, I just need to send down the flag to JIT down to the
workers. Will look at it tomorrow. If you want to measure / play around
till then you can manually hack the PGJIT_* checks in execExprCompile.c

with that done, on my laptop, tpch-Q01, scale 10:

SET max_parallel_workers_per_gather=0; SET jit_expressions = 1;
15145.508 ms
SET max_parallel_workers_per_gather=0; SET jit_expressions = 0;
23808.809 ms
SET max_parallel_workers_per_gather=4; SET jit_expressions = 1;
4775.170 ms
SET max_parallel_workers_per_gather=4; SET jit_expressions = 0;
7173.483 ms

(that's with inlining and deforming enabled too)

Greetings,

Andres Freund

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