From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: effect of JIT tuple deform? |
Date: | 2018-06-26 19:25:54 |
Message-ID: | CAFj8pRCs09eW=D3m0z2Jv1fqJZQ_2ii4AUt8ZUhFJqr7KiS3aw@mail.gmail.com |
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Lists: | pgsql-hackers |
Hi
I played with it and maybe I got interesting result.
When I played with really big table, then I got IO waits and effect of
jit_tuple_deforming is near to zero (as expected)
When I played with smaller table under RAM, then I can see positive effect
of JIT_TD, but only when optimization is active. When optimization was
false, then JIT_TD has negative slowdown.
Shared buffers 1GB
table wt .. 100columns, 2M rows, cca 823MB
set max_parallel_workers to 0;
query:
select sum(c99) from wt;
default (jit active) ... 1853ms
set jit_tuple_deforming to off .. 1397ms
set jit off .. 1400ms
== enforced inline ==
jit_tuple_deforming on .. 1610ms
jit_tuple_deforming off .. 1420ms
== enforced optimize ==
jit_tuple_deforming on .. 842ms
jit_tuple_deforming off .. 1420ms
I played with setting and I got the best speed with
jit_inline_above_cost ..some pretty high number
jit_optimize_above_cost 0
jit_tuple_deforming on
So I am able to see effect of jit_tuple_deforming, and very well, but only
if optimization is active. When optimization is not active then
jit_tuple_deforming does slowdown.
So maybe a usage of jit_tuple_deforming can be conditioned by
jit_optimization?
Regards
Pavel
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