* Rafael J. Wysocki <r...@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
> > <torva...@linux-foundation.org> wrote:
> > > On Tue, Nov 14, 2017 at 3:53 PM, Thomas Gleixner <t...@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 <mi...@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
