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From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "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 09:47:11 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1711150943030.1805@nanos> (raw)
In-Reply-To: <CA+55aFw=JkvmxohBtVy-3QPtFibq_rv_uqp3ss+gpo8vSqYGQw@mail.gmail.com>

On Tue, 14 Nov 2017, Linus Torvalds 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.
> 

Tired brain did not connect it to the revert.

On that machine with ea0ee3398877: Revert "x86: CPU: Fix up "cpu MHz" in
/proc/cpuinfo" reverted it takes:

real	0m4.497s
user	0m0.012s
sys	0m0.000s

> It sounds like the current patch is slower, but likely acceptable
> considering that you get the right results now ..

Correct and the factor 10, i.e. 30ms vs. 3ms is not horrible, while the 4.5
seconds are.

Thanks,

	tglx

  parent reply	other threads:[~2017-11-15  8:47 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-09 10:38 [PATCH] x86: use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz" again WANG Chao
2017-11-09 16:06 ` Rafael J. Wysocki
2017-11-09 22:30   ` Rafael J. Wysocki
2017-11-10  0:06     ` Rafael J. Wysocki
2017-11-10  4:04       ` WANG Chao
2017-11-10  4:11         ` WANG Chao
2017-11-10 19:11     ` Linus Torvalds
2017-11-10 23:09       ` Rafael J. Wysocki
2017-11-14 22:47         ` Rafael J. Wysocki
2017-11-14 23:02           ` Linus Torvalds
2017-11-14 23:53             ` Thomas Gleixner
2017-11-15  0:04               ` Linus Torvalds
2017-11-15  0:06                 ` Linus Torvalds
2017-11-15  0:30                   ` Rafael J. Wysocki
2017-11-15  0:34                     ` Linus Torvalds
2017-11-15  1:13                       ` [PATCH] x86 / CPU: Always show current CPU frequency in /proc/cpuinfo Rafael J. Wysocki
2017-11-15  8:47                         ` Thomas Gleixner
2017-11-15  9:33                         ` WANG Chao
2017-11-16  0:24                           ` Rafael J. Wysocki
2017-11-16  9:50                             ` WANG Chao
2017-11-16 13:54                               ` Rafael J. Wysocki
2017-11-17  4:27                                 ` WANG Chao
2017-11-17 13:33                                   ` Rafael J. Wysocki
2017-11-15  7:43                     ` [PATCH] x86: use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz" again Ingo Molnar
2017-11-15  7:54                       ` Greg Kroah-Hartman
2017-11-15 17:27                       ` Linus Torvalds
2017-11-15 18:05                         ` Thomas Gleixner
2017-11-15  8:47                 ` Thomas Gleixner [this message]
2017-11-15  0:06               ` Rafael J. Wysocki
2017-11-10  7:25   ` Ingo Molnar
2017-11-10  9:21     ` WANG Chao

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