Re: Optimizing PostgreSQL with LLVM's PGO+LTO
| От | João Paulo Labegalini de Carvalho |
|---|---|
| Тема | Re: Optimizing PostgreSQL with LLVM's PGO+LTO |
| Дата | |
| Msg-id | CAGjvy2-a-j+KyxR34=k5ReRZqSHq1MmRv+aULNi6Td8WiO7SSw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Optimizing PostgreSQL with LLVM's PGO+LTO (Andres Freund <andres@anarazel.de>) |
| Ответы |
Re: Optimizing PostgreSQL with LLVM's PGO+LTO
|
| Список | pgsql-hackers |
What compiler / version / flags / OS did you try?
I am running experiment on a machine with:
- Intel(R) Xeon(R) Platinum 8268 CPU @ 2.90GHz
- Ubuntu 18.04.6 LTS
- LLVM/Clang 15.0.6 (build from source)
These are the flags I am using:
CFLAGS = -O3 -fuse-ld=lld -gline-tables-only -fprofile-instr-generate
LDFLAGS = -fuse-ld=lld -Wl,-q
CFLAGS = -O3 -fuse-ld=lld -gline-tables-only -fprofile-instr-generate
LDFLAGS = -fuse-ld=lld -Wl,-q
FWIW, I've experimented with LTO and PGO a bunch, both with gcc and clang. I
did hit a crash in gcc, but that did turn out to be a compiler bug, and
actually reduced to something not even needing LTO.
Good to hear that it works. I just need to figure out what is going wrong on my end then.
I saw quite substantial speedups with PGO, but I only tested very specific
workloads. IIRC it was >15% gain in concurrent readonly pgbench.
I successfully applied PGO only and obtained similar gains with TPC-C & TPC-H workloads.
I dimly recall failing to get some benefit out of bolt for some reason that I
unfortunately don't even vaguely recall.
I got similar gains slightly higher than PGO with BOLT, but not for all queries in TPC-H. In fact, I observed small (2-4%) regressions with BOLT.
João Paulo L. de Carvalho
Ph.D Computer Science | IC-UNICAMP | Campinas , SP - Brazil
Postdoctoral Research Fellow | University of Alberta | Edmonton, AB - Canada
Ph.D Computer Science | IC-UNICAMP | Campinas , SP - Brazil
Postdoctoral Research Fellow | University of Alberta | Edmonton, AB - Canada
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