Re: Avoid stack frame setup in performance critical routines using tail calls

David Rowley <dgrowleyml@gmail.com>

From: David Rowley <dgrowleyml@gmail.com>

To: Andres Freund <andres@anarazel.de>

Cc: PostgreSQL Development <pgsql-hackers@postgresql.org>, Robert Haas <robertmhaas@gmail.com>, Michael Paquier <michael.paquier@gmail.com>, Tomas Vondra <tv@fuzzy.cz>

Date: 2021-07-20T07:37:46Z

Lists: pgsql-hackers

Attachments

AllocSetAlloc_clang.txt (text/plain)
palloc_clang.txt (text/plain)
percent_clang.txt (text/plain)

On Tue, 20 Jul 2021 at 19:04, Andres Freund <andres@anarazel.de> wrote:
> > * AllocateSetAlloc.txt
> > * palloc.txt
> > * percent.txt
>
> Huh, that's interesting. You have some control flow enforcement stuff turned on (the endbr64). And it looks like it has a non zero cost (or maybe it's just skid). Did you enable that intentionally? If not, what compiler/version/distro is it? I think at least on GCC that's -fcf-protection=...

It's ubuntu 21.04 with gcc 10.3 (specifically gcc version 10.3.0
(Ubuntu 10.3.0-1ubuntu1)

I've attached the same results from compiling with clang 12
(12.0.0-3ubuntu1~21.04.1)

David

Commits

Optimize GenerationAlloc() and SlabAlloc()
- a0cd95448067 17.0 landed
Refactor AllocSetAlloc(), separating hot and cold paths
- 413c18401dcc 17.0 landed
Adjust memory allocation functions to allow sibling calls
- 743112a2e993 17.0 landed