rtc: lost some interrupts at 1024Hz.

rtc: lost some interrupts at 1024Hz.

[Tomasz Chmielewski]

Whenever I start a guest, I get kernel log filled with "rtc: lost some 
interrupts at 1024Hz".

What's the reason for it?


I searched the archives, and it looks that this problem did already 
happen for a couple of people.

Also in my case, it looks that KVM is not the problem here, but Qemu.


Searching Qemu forums revealed one such report with no reply[1].

Searching Qemu-devel list revealed one report, with no solution[2]

Because of that, the performance is really bad.

Is there a solution for that? I use kvm-intel, if needed, I can attach 
kernel .config.


[1] http://qemu-forum.ipi.fi/viewtopic.php?t=1468
[2] http://lists.gnu.org/archive/html/qemu-devel/2006-07/threads.html#00193


-- 
Tomasz Chmielewski
http://wpkg.org

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Re: rtc: lost some interrupts at 1024Hz.

[Anthony Liguori]

Tomasz Chmielewski wrote:
> Whenever I start a guest, I get kernel log filled with "rtc: lost some 
> interrupts at 1024Hz".
>   

Does rebooting the host machine with nolapic on the kernel command line 
help?

What sort of system are you using?

Regards,

Anthony Liguori

> What's the reason for it?
>
>
> I searched the archives, and it looks that this problem did already 
> happen for a couple of people.
>
> Also in my case, it looks that KVM is not the problem here, but Qemu.
>
>
> Searching Qemu forums revealed one such report with no reply[1].
>
> Searching Qemu-devel list revealed one report, with no solution[2]
>
> Because of that, the performance is really bad.
>
> Is there a solution for that? I use kvm-intel, if needed, I can attach 
> kernel .config.
>
>
> [1] http://qemu-forum.ipi.fi/viewtopic.php?t=1468
> [2] http://lists.gnu.org/archive/html/qemu-devel/2006-07/threads.html#00193
>
>
>   


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Re: rtc: lost some interrupts at 1024Hz.

[Tomasz Chmielewski]

Anthony Liguori schrieb:
> Tomasz Chmielewski wrote:
>> Whenever I start a guest, I get kernel log filled with "rtc: lost some 
>> interrupts at 1024Hz".
>>   
> 
> Does rebooting the host machine with nolapic on the kernel command line 
> help?

It turned out, this option needs to be enabled:

Processor type and features  --->
    [*] Provide RTC interrupt

(or CONFIG_HPET_EMULATE_RTC=y in .config).


With it enabled, I don't have these messages anymore, and performance is 
much much better.


> What sort of system are you using?

# uname -a
Linux syn5 2.6.21-rc6 #3 SMP Fri Apr 13 16:37:31 CEST 2007 x86_64 
Intel(R) Xeon(R) CPU            3050  @ 2.13GHz GNU/Linux

KVM-18.


-- 
Tomasz Chmielewski
http://wpkg.org

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