Horton

Re: JIT compiling with LLVM v11

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-09T21:08:36Z
Lists: pgsql-hackers 
On 2018-03-09 15:42:24 -0500, Peter Eisentraut wrote:
> For jit_optimize_above_cost, in my testing, any query where JIT payed
> off was even faster with optimizing.  So right now I don't see a need to
> make this a separate setting.  Maybe just make it an on/off setting for
> experimenting.

I'd prefer to be more defensive here. The time needed for JITing without
optimization is roughly linear, whereas optimization is definitely not
linear with input size.


> For inlining, I haven't been able to get a clear picture.  It's a bit
> faster perhaps, but the optimizing dominates it.  I don't have a clear
> mental model for what kind of returns to expect from this.

Yea, you need longrunning queries to benefit significantly. There's a
*lot* more potential once some structural issues with the expression
format (both with and without JIT) are fixed.


> What I'd quite like is if EXPLAIN or EXPLAIN ANALYZE showed something
> about what kind of JIT processing was done, if any, to help with this
> kind of testing.

Yea, I like that. I think we can only show that when timing is on,
because otherwise the tests will not be stable depending on --with-jit
being specified or not.

So I'm thinking of displaying it similar to the "Planning time" piece,
i.e. depending on es->summary being enabled. It'd be good to display the
inline/optimize/emit times too. I think we can just store it in the
JitContext. But the inline/optimize/emission times will only be
meaningful when the query is actually executed, I don't see a way around
that...

Greetings,

Andres Freund

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".