linux-kernel - Re: [PATCH] x86: use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz" again

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Date:   Wed, 15 Nov 2017 00:53:24 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        WANG Chao <chao.wang@...oud.cn>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Mathias Krause <minipli@...glemail.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH] x86: use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz"
 again

On Tue, 14 Nov 2017, Linus Torvalds wrote:

> On Tue, Nov 14, 2017 at 2:47 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> >
> > So what about the one below?  It works for me as expected.
> 
> Can somebody with 100+ cores test this? Ingo? You had a 160 core
> machine that took forever, didn't you..

On a 144 CPUs machine:

time cat /proc/cpuinfo >/dev/null

Current head:

real	0m0.003s
user	0m0.000s
sys	0m0.002s

Current head + Raphaels patch:

real	0m0.029s
user	0m0.000s
sys	0m0.010s

So that patch is actually slower.

Thanks,

	tglx