From: "Rafał Miłecki" <rafal@milecki.pl>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Rabin Vincent <rabin.vincent@axis.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Srinivas Kandagatla <srinivas.kandagatla@gmail.com>,
tglx@linutronix.de, Patrice Chotard <patrice.chotard@st.com>,
Hauke Mehrtens <hauke@hauke-m.de>
Subject: Re: DIfferent BogoMIPS value after bbaa06702719 ("clocksource/drivers/arm_global_timer: Register delay timer")
Date: Thu, 2 Mar 2017 18:46:10 +0100 [thread overview]
Message-ID: <8d136a2c-c306-e8c8-780a-f55cb891f6e0@milecki.pl> (raw)
In-Reply-To: <20170302141334.GM21222@n2100.armlinux.org.uk>
On 03/02/2017 03:13 PM, Russell King - ARM Linux wrote:
> On Thu, Mar 02, 2017 at 02:36:23PM +0100, Rafał Miłecki wrote:
>> Hi,
>>
>> I just updated kernel on my SmartRG SR400ac (bcm4708-smartrg-sr400ac.dts) from
>> 4.4 to 4.9 and noticed that this part of the log:
>> [ 0.020820] Calibrating delay loop... 1594.16 BogoMIPS (lpj=7970816)
>> (...)
>> [ 0.190806] Brought up 2 CPUs
>> [ 0.200022] SMP: Total of 2 processors activated (3188.32 BogoMIPS).
>>
>> became:
>> [ 0.027082] Calibrating delay loop (skipped), value calculated using timer frequency.. 800.00 BogoMIPS (lpj=4000000)
>> (...)
>> [ 0.078858] Brought up 2 CPUs
>> [ 0.088254] SMP: Total of 2 processors activated (1600.00 BogoMIPS).
>>
>> This is caused by commit bbaa06702719 ("clocksource/drivers/arm_global_timer:
>> Register delay timer").
>>
>> Is this something expected?
>
> Yes.
>
>> Or should I be worried about this? I'm aware it's just BogoMIPS, but I
>> still prefer to ask :)
>
> It's *bogus*. Bogomips is the calibration value that the kernel uses
> to achieve delays. It has nothing to do with the speed of the CPU on
> modern systems that use a timer instead. (In that case, it's a
> calibration value for the timer, rather than a calibration value for
> the number of software loops required to achieve a delay.)
Now I can sleep calm ;) thanks!
next prev parent reply other threads:[~2017-03-02 20:31 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-02 13:36 Rafał Miłecki
2017-03-02 14:13 ` Russell King - ARM Linux
2017-03-02 17:46 ` Rafał Miłecki [this message]
2017-03-02 14:13 ` Rabin Vincent
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