CachyOS does compile packages with the x86-64-v3, x86-64-v4 and Zen4 instruction set and LTO to provide a higher performance. Core packages also get PGO or BOLT optimization.
CachyOS utilizes the BORE Scheduler for better interactivity, and offers a variety of scheduler options including EEVDF, sched-ext, ECHO, and RT. All kernels are compiled with optimized x86-64-v3, x86-64-v4, Zen4 instructions and LTO to be optimized for your CPU.
I like the sound of that for my new gaming distro, but I really feel more comfortable in the .deb ecosystem.
Depending on the exact flags, some workloads will be faster, some will be identical, and some will be slower. Compilier optimization is some dark magic that relies on a ton of factors, but you can’t just assume that going from like -O2 to -O3 will provide better performance, since the optimizations also rely on the underlying code as to what they’ll actually make happen… and is why, for the most part, everyone suggests you stop at -O2 since you can start getting unexpected behavior the further up the curve you go.
And we’re talking low single digit performance improvements at best, not anything that anyone who is doing anything that’s not running benchmarks 24/7 would ever even notice in real world performance.
Disclaimer: there are workloads that are going to show different performance uplifts, but we’re talking Firefox and KDE and games here, per the OP’s comments.
Also they do default to a different scheduler, which is almost certainly why anyone using it will notice it feels “faster”, but it’s mainlined in the kernel so it’s not like you can’t use that anywhere else.
While this is broadly true,
-O3doesn’t have as many downsides as it used to, so some distributions are considering to move to it (like Ubuntu).It was a mess in the early days, though, with not just performance issues but outright crashing being a common problem.