Re: performance regressions in 15.0

From: Rozhuk Ivan <rozhuk.im_at_gmail.com>
Date: Mon, 08 Dec 2025 12:18:48 UTC 
On Mon, 8 Dec 2025 13:38:57 +0200
Konstantin Belousov <kib@freebsd.org> wrote:

> But there are other benefits from linking the libraries dynamically.
> E.g. the same (?) user shed crocodile tears over memory usage by 64bit
> system, and linking libllvm dynamically exactly reduces the memory
> profile by sharing significant part of text for cc, lld, and minor
> binutils.
> 

User can buy more ram but can not buy more time/speed. (in case single thread configure/build)

Also, it looks like even dyn linked llvm can work faster: I do some additional bencharks
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=287447
and dyn linked devel/llvm19 work 4+x faster than dyn linked llvm from base.
(that is the reason that no one report before that it works very slow - it is less than 2x slower that it can be)

Probably in base llvm have some PIE/addr randomisation enabled that drop down speed dramatically: -4x in some case.