Horton

Re: JIT compiling with LLVM v9.0

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Merlin Moncure <mmoncure@gmail.com>, Konstantin Knizhnik <k.knizhnik@postgrespro.ru>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-02-13T18:50:43Z
Lists: pgsql-hackers 
On 2018-02-13 13:43:40 -0500, Robert Haas wrote:
> On Sun, Feb 11, 2018 at 10:00 AM, Merlin Moncure <mmoncure@gmail.com> wrote:
> > I tested several queries in my application that had >30 second compile
> > times against a one second run time,.  Not being able to manage when
> > compilation happens is making it difficult to get a sense of llvm
> > performance in the general case.
> 
> In theory, the GUCs Andres has added to only compile if the estimated
> total cost is above some threshold is supposed to help with this.

Note that the GUCs as posted are set *way* too low, they're currently
toy thresholds. That's easier for testing, but I guess I should set them
to something better.

It's not unrealistic to expect them to be insufficient however - the
overhead roughly linearly grows with the number of expressions, which
might not reflect the gain equally.


> How did you manage to create an expression that took 30 seconds to
> compile?  It doesn't take that long to compile a 5000-line C file.

Any chance a debug build of LLVM was used? The overhead of that are
easily an order of magnitude or more.

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".