> > On 12/12/19 9:10 AM, Justin Forbes wrote: > > > On Thu, Dec 12, 2019 at 3:48 AM Peter Robinson <pbrobinson@xxxxxxxxx> wrote: > > >> > > >> Hey All. > > >> > > >> In digging through some pieces around CPU_IDLE I noticed that > > >> NO_HZ_IDLE is explicitly disabled on x86_64 but not on all other > > >> architectures. > > >> > > >> Doing a "git log --follow > > >> configs/fedora/generic/x86/x86_64/CONFIG_NO_HZ_IDLE" it goes all the > > >> way back to 2016 when we changed the way the configs were handled. > > >> > > >> The upstream kernel's opinion [1] on it is "Most of the time you want > > >> to say Y here." so I'm wondering if there's a reason why we're > > >> difference on x86_64 or is it just lost in the winds of time? > > >> > > >> Peter > > >> > > >> PS was digging around CPU_IDLE_GOV_TEO for those curious. > > >> > > >> [1] https://cateee.net/lkddb/web-lkddb/NO_HZ_IDLE.html > > > > > > > > > commit 3836faf6e68495fc70316229a3540506f7ce4c98 > > > Author: Kyle McMartin <kyle@xxxxxxxxxxxxxxxxx> > > > Date: Wed Sep 17 13:10:12 2014 -0500 > > > > > > re-enable RCU_FAST_NO_HZ, enable NO_HZ_FULL on x86_64 > > > > > > - I also like to live dangerously. (Re-enable RCU_FAST_NO_HZ which > > > has been off > > > since April 2012. Also enable NO_HZ_FULL on x86_64.) > > > > Yeah I wouldn't quite say it's been "lost" but the real question > > is if it still makes sense. I don't have a strong opinion without > > data. Prarit, any opinion here? > > Oh, I wasn't pointing out that it wasn't just lost, I was pointing out > that NO_HZ_IDLE is not set because we run NO_HZ_FULL. We were one of > the first distros to do so, and it has worked well for us. I have a > fairly strong opinion about not dropping back to IDLE without good > reason. This wasn't a proposal to change anything here at all, sorry if that was the way it read. I was purely wondering, while digging through stuff around cpu idle, for the difference between arches. With the hit around NO_HZ_IDLE vs NO_HZ_FULL I dug some more and basically it seems the reason we don't have the later on the non x86_64 arches is because for some reason we unset VIRT_CPU_ACCOUNTING_GEN for all except x86_64, it looks to be historical, all our current architectures now look to support that option. Anyone aware of any reason we shouldn't use the NO_HZ_FULL/VIRT_CPU_ACCOUNTING_GEN as standard across all arches? P _______________________________________________ kernel mailing list -- kernel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to kernel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/kernel@xxxxxxxxxxxxxxxxxxxxxxx
