Horton

Re: JIT compiling with LLVM v12

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

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Noah Misch <noah@leadboat.com>, Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org
Date: 2018-08-22T14:36:00Z
Lists: pgsql-hackers 
On 22/08/2018 08:20, Noah Misch wrote:
> Regardless of the choice of jit={on|off} default, these numbers tell me that
> some or all of jit_*_cost defaults are too low.

That was also my earlier analysis.

I'm suspicious that we haven't had much feedback about this.  We've
heard of one or two cases where LLVM broke a query outright, and that
was fixed and that was a good result.  But we haven't heard anything
about performance regressions.  Surely there must be some.  There hasn't
been any discussion or further analysis of the default cost settings
either.  I feel that we don't have enough information.

Another problem is that LLVM is only enabled in some versions of
packages.  For example, in the PGDG RPMs, it's enabled for RHEL 7 but
not RHEL 6.  So you could be in for a surprise if you upgrade your
operating system at some point.

I would like, however, that we make a decision one way or the other
before the next beta.  I've been handwaving a bit to users not to rely
on the current betas for performance testing because the defaults might
change later.  That's bad either way.

-- 
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".