From: Avi Kivity <avi@redhat.com>
To: Sebastian Hetze <s.hetze@linux-ag.com>
Cc: kvm@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: Strange CPU usage pattern in SMP guest
Date: Sun, 21 Mar 2010 17:17:38 +0200 [thread overview]
Message-ID: <4BA63892.6090006@redhat.com> (raw)
In-Reply-To: <20100321145548.CC027A0015@mail.linux-ag.de>
On 03/21/2010 04:55 PM, Sebastian Hetze wrote:
> On Sun, Mar 21, 2010 at 02:19:40PM +0200, Avi Kivity wrote:
>
>> On 03/21/2010 02:02 PM, Sebastian Hetze wrote:
>>
>>> 12:46:02 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle
>>> 12:46:03 all 0,20 11,35 10,96 8,96 0,40 2,99 0,00 0,00 65,14
>>> 12:46:03 0 1,00 11,00 7,00 15,00 0,00 1,00 0,00 0,00 65,00
>>> 12:46:03 1 0,00 7,14 2,04 6,12 1,02 11,22 0,00 0,00 72,45
>>> 12:46:03 2 0,00 15,00 1,00 12,00 0,00 1,00 0,00 0,00 71,00
>>> 12:46:03 3 0,00 11,00 23,00 8,00 0,00 0,00 0,00 0,00 58,00
>>> 12:46:03 4 0,00 0,00 50,00 0,00 0,00 0,00 0,00 0,00 50,00
>>> 12:46:03 5 0,00 13,00 20,00 4,00 0,00 1,00 0,00 0,00 62,00
>>>
>>> So it is only CPU4 that is showing this strange behaviour.
>>>
>>>
>> Can you adjust irqtop to only count cpu4? or even just post a few 'cat
>> /proc/interrupts' from that guest.
>>
>> Most likely the timer interrupt for cpu4 died.
>>
> I've added two keys +/- to your irqtop to focus up and down
> in the row of available CPUs.
> The irqtop for CPU4 shows a constant number of 6 local timer interrupts
> per update, while the other CPUs show various higher values:
>
> irqtop for cpu 4
>
> eth0 188
> Rescheduling interrupts 162
> Local timer interrupts 6
> ata_piix 3
> TLB shootdowns 1
> Spurious interrupts 0
> Machine check exceptions 0
>
>
> irqtop for cpu 5
>
> eth0 257
> Local timer interrupts 251
> Rescheduling interrupts 237
> Spurious interrupts 0
> Machine check exceptions 0
>
> So the timer interrupt for cpu4 is not completely dead but somehow
> broken.
That is incredibly weird.
> What can cause this problem? Any way to speed it up again?
>
The host has 8 cpus and is only running this 6 vcpu guest, yes?
Can you confirm the other vcpus are ticking at 250 Hz?
What does 'top' show running on cpu 4? Pressing 'f' 'j' will add a
last-used-cpu field in the display.
Marcelo, any ideas?
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2010-03-21 15:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-21 0:13 Strange CPU usage pattern in SMP guest Sebastian Hetze
2010-03-21 10:09 ` Avi Kivity
2010-03-21 12:02 ` Sebastian Hetze
[not found] ` <20100321120236.55228A0015@mail.linux-ag.de>
2010-03-21 12:19 ` Avi Kivity
2010-03-21 14:55 ` Sebastian Hetze
[not found] ` <20100321145548.CC027A0015@mail.linux-ag.de>
2010-03-21 15:17 ` Avi Kivity [this message]
2010-03-21 15:47 ` Sebastian Hetze
2010-03-22 12:51 ` Sebastian Hetze
2010-03-23 21:18 ` Marcelo Tosatti
2010-03-30 8:27 ` Sebastian Hetze
[not found] ` <20100330082743.49A113030135@mail.linux-ag.de>
2010-04-05 21:24 ` Sebastian Hetze
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