Messages in this thread | | | Date | Wed, 15 Nov 2017 08:43:58 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz" again |
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* Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Wednesday, November 15, 2017 1:06:12 AM CET Linus Torvalds wrote: > > On Tue, Nov 14, 2017 at 4:04 PM, Linus Torvalds > > <torvalds@linux-foundation.org> wrote: > > > On Tue, Nov 14, 2017 at 3:53 PM, Thomas Gleixner <tglx@linutronix.de> wrote: > > >> Current head + Raphaels patch: > > >> > > >> real 0m0.029s > > >> user 0m0.000s > > >> sys 0m0.010s > > >> > > >> So that patch is actually slower. > > > > > > Oh it definitely is expected to be slower, because it does the IPI to > > > all the cores and actually gets their frequency right. > > > > > > It was the old one that we had to revert (because it did so > > > sequentially) that was really bad, and took something like 2+ seconds > > > on Ingo's 160-core thing, iirc. > > > > Looked it up. Ingo's machine "only" had 120 cores, and he said > > > > fomalhaut:~> time cat /proc/cpuinfo >/dev/null > > real 0m2.689s > > > > for the bad serial case, so yeah, it looks "a bit" better than it was ;) > > OK, so may I queue it up? > > I don't think I can get that to work substantially faster anyway ...
The new version is OK I suppose:
Acked-by: Ingo Molnar <mingo@kernel.org>
I also think that /proc/cpuinfo is a pretty bad interface for many uses - I personally only very rarely need the cpuinfo of _all_ CPUs.
We we should eventually have /proc/cpu/N/info or so, so that 99% of the times cpuinfo is needed to report bugs we can do:
cat /proc/cpu/0/info
With maybe also the following variants:
/proc/cpu/first/ /proc/cpu/last/ /proc/cpu/current/
... to the first/last/current CPUs.
Thanks,
Ingo
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