Horton

Re: JIT compiling with LLVM v11

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-11T17:19:57Z
Lists: pgsql-hackers 
On 3/9/18 15:56, Andres Freund wrote:
> On 2018-03-09 15:28:19 -0500, Peter Eisentraut wrote:
>> On 3/6/18 15:16, Andres Freund wrote:
>>> 2) Don't load the JIT provider until fully needed. Right now
>>>    jit_compile_expr() will load the jit provider even if not really
>>>    needed. We should probably move the first two return blocks in
>>>    llvm_compile_expr() into jit_compile_expr(), to avoid that.
>>
>> I see that you have implemented that, but it doesn't seem to have helped
>> with my make installcheck times.
> 
> What's the exact comparison you're looking at?

I'm just running `time make installcheck` with default settings, as
described in my message from March 6.

> I think that's largely that unnecessary trivial queries get JITed and
> optimized, because the stats are entirely completely off.

Right.  I instrumented this a bit, and there are indeed two handfuls of
queries that exceed the default JIT thresholds, as well as a few that
trigger JIT because they disable some enable_* planner setting, as
previously discussed.

Should we throw in some ANALYZEs to avoid this?

If I set jit_expressions = off, then the timings match again.

It's perhaps a bit confusing that some of the jit_* settings take effect
at plan time and some at execution time.  At the moment, this mainly
affects me reading the code ;-), but it would also have some effect on
prepared statements and such.

Also, jit_tuple_deforming is apparently used only when jit_expressions
is on.

So, we should work toward more clarity on all these different settings,
what they are useful for, when to set them, how they interact.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Improve JIT docs.

  2. Add documentation for the JIT feature.

  3. Add EXPLAIN support for JIT.

  4. Add inlining support to LLVM JIT provider.

  5. JIT tuple deforming in LLVM JIT provider.

  6. Add FIELDNO_* macro designating offset into structs required for JIT.

  7. Add expression compilation support to LLVM JIT provider.

  8. Expand list of synchronized types and functions in LLVM JIT provider.

  9. Add helpers for emitting LLVM IR.

  10. Basic planner and executor integration for JIT.

  11. Debugging and profiling support for LLVM JIT provider.

  12. Support for optimizing and emitting code in LLVM JIT provider.

  13. Add file containing extensions of the LLVM C API.

  14. Basic JIT provider and error handling infrastructure.

  15. Add configure infrastructure (--with-llvm) to enable LLVM support.

  16. Add C++ support to configure.

  17. Add PGAC_PROG_VARCC_VARFLAGS_OPT autoconf macro.

  18. Fix VM buffer pin management in heap_lock_updated_tuple_rec().

  19. Allow tupleslots to have a fixed tupledesc, use in executor nodes.

  20. Expression evaluation based aggregate transition invocation.

  21. Perform slot validity checks in a separate pass over expression.

  22. Rely on executor utils to build targetlist for DML RETURNING.

  23. Refer to OS X as "macOS", except for the port name which is still "darwin".