Sv: Re: Query is over 2x slower with jit=on

Andreas Joseph Krogh <andreas@visena.com>

From: Andreas Joseph Krogh <andreas@visena.com>

To: pgsql-hackers@lists.postgresql.org

Date: 2018-04-18T16:26:03Z

Lists: pgsql-hackers

På onsdag 18. april 2018 kl. 17:50:55, skrev Andres Freund <andres@anarazel.de 
<mailto:andres@anarazel.de>>:
On 2018-04-18 17:35:31 +0200, Andreas Joseph Krogh wrote:
 > With jit=on:
 > https://explain.depesz.com/s/vYB
 > Planning Time: 0.336 ms
 >  JIT:
 >   Functions: 716
 >   Generation Time: 78.404 ms
 >   Inlining: false
 >   Inlining Time: 0.000 ms
 >   Optimization: false
 >   Optimization Time: 43.916 ms
 >   Emission Time: 600.031 ms

 Any chance this is a debug LLVM build?

 > What's the deal with jit making it slower?

 JIT has cost, and sometimes it's not beneficial. Here our heuristics
 when to JIT appear to be a bit off. In the parallel world it's worse
 because the JITing is duplicated for parallel workers atm.

PostgreSQL is built with "--enable-debug --with-llvm". LLVM is the one which 
comes with Ubuntu-17.10.

-- Andreas Joseph Krogh
CTO / Partner - Visena AS
Mobile: +47 909 56 963
andreas@visena.com <mailto:andreas@visena.com>
www.visena.com <https://www.visena.com>
 <https://www.visena.com>

Commits

Fix issues around EXPLAIN with JIT.
- e97c4d967ba5 11.0 landed
- c03c1449c092 12.0 landed
Collect JIT instrumentation from workers.
- e63441c3f5ca 11.0 landed
- 33001fd7a707 12.0 landed
Make EXPLAIN output for JIT compilation more dense.
- 6859bd2632d8 11.0 landed
- 52050ad8ebec 12.0 landed
Save/restore SPI's global variables in SPI_connect() and SPI_finish().
- 825f10fbda7a 11.0 cited
Rationalize handling of single and double quotes in bootstrap data.
- 55d26ff638f0 11.0 cited