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

From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	WANG Chao <chao.wang@ucloud.cn>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Vikas Shivappa <vikas.shivappa@linux.intel.com>,
	Kate Stewart <kstewart@linuxfoundation.org>,
	Len Brown <len.brown@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Mathias Krause <minipli@googlemail.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: [PATCH] x86: use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz" again
Date: Wed, 15 Nov 2017 19:05:22 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1711151903260.1805@nanos> (raw)
In-Reply-To: <CA+55aFzHqhxzv1p7fqdXPugMUVRyM44pL4KO3f_T6yFJUACXvw@mail.gmail.com>

On Wed, 15 Nov 2017, Linus Torvalds wrote:
> On Tue, Nov 14, 2017 at 11:43 PM, Ingo Molnar <mingo@kernel.org> wrote:
> Again, try that "cat" example again, and time it.
> 
> (And yes, I also know that "cpu*/cpufreq" is a symlink, but the direct
> names are illogical, and no faster for me. Try it if you like:
> 
>   time cat /sys/devices/system/cpu/cpufreq/policy*/scaling_cur_freq > /dev/null

Just for the fun of it I tried. It's exactly the same time as /proc/cpuinfo
with the reverted patch which did the full IPI thing, i.e. >4 seconds on
that machine.

Not a surprise because those files do the full IPI thing as well.

Thanks,

	tglx