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

På onsdag 18. april 2018 kl. 18:26:03, skrev Andreas Joseph Krogh <
andreas@visena.com <mailto:andreas@visena.com>>:
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.
 
Some more info;
 
Without --enable-debug (seems this didn't impact performance mutch):
 
First 5 executions (prepared-statement issued from psql)
 Planning Time: 47.634 ms
  JIT:
    Functions: 725
    Generation Time: 74.748 ms
    Inlining: true
    Inlining Time: 90.763 ms
    Optimization: true
    Optimization Time: 5822.516 ms
    Emission Time: 3089.127 ms
  Execution Time: 16375.996 ms
 
 
After 5 executions (prepared-statement issued from psql)
Planning Time: 0.385 ms
 JIT:
   Functions: 716
   Generation Time: 76.382 ms
   Inlining: false
   Inlining Time: 0.000 ms
   Optimization: false
   Optimization Time: 41.709 ms
   Emission Time: 613.074 ms
 Execution Time: 2031.830 ms
 
jit=off:
 
Planning Time: 0.171 ms
 Execution Time: 832.489 ms
 
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