Messages in this thread | | | From | Uros Bizjak <> | Date | Mon, 12 Sep 2022 11:26:27 +0200 | Subject | Re: [PATCH v2 RESEND] locking/lockref/x86: Enable ARCH_USE_CMPXCHG_LOCKREF for X86_CMPXCHG64 |
| |
On Sat, Sep 10, 2022 at 7:23 PM Linus Torvalds <torvalds@linux-foundation.org> wrote: > > On Sat, Sep 10, 2022 at 2:28 AM Uros Bizjak <ubizjak@gmail.com> wrote: > > > > May I consider this message as a formal Acked-by: for the patch? I'll > > resubmit the patch with a commit message updated to reference > > lockref_put_not_zero instead of the removed lockref_get_or_lock. > > Sure, sounds good to me. > > It would be particularly nice if you can also see any change in > performance numbers - but that simply may not be possible. > > 32-bit x86 tends to also be very low core count, so the whole lockref > thing may or may not be measurable (no practical contention on the > lock), but the code certainly seems to get better.
I tested this patch on an old core-2 duo in 32-bit mode, mainly to test my try_cmpxchg64 patch on 32-bit targets. There were no observable changes in the run time, but we are talking about a two-core system here. OTOH, there were considerable code-size savings, as noticed in my patch submission entry.
Please also note, that I am aware that changes to the default configuration of 32-bit falls into the vintage computing nowadays. However, a couple of enthusiast old-timers would still like to squeeze some more juice out of their old rigs (e.g. m68k, alpha and x86-32) by using all available processor infrastructure. OTOH, I don't want to burden x86 maintainers with my hobby, but here we are talking about such low-hanging fruit that it warrants the one-line change. By the same patch, the default config can be cleaned a bit and made a bit more consistent also for x86_64.
Thanks, Uros.
| |