[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] Problems with enabling hypervisor C and P-state control

  • To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
  • From: "Niraj Tolia" <ntolia@xxxxxxxxx>
  • Date: Mon, 27 Oct 2008 19:19:41 -0700
  • Cc: "Liu, Jinsong" <jinsong.liu@xxxxxxxxx>, Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Yu, Ke" <ke.yu@xxxxxxxxx>
  • Delivery-date: Mon, 27 Oct 2008 19:20:18 -0700
  • Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=ah2xhQbZ5V24fRSwVduoY6uwnsR8tM8+fu4ZrY45ngjC2TcluiKrk7VMExs5jCY0AB QMKwIy+bziEhiq4BLH/zu2eXUgEVqXL/y38ycX7yzzJvG9deLHxEOBlL30zQ0TEsZDO4 RJkfUVntHVz1XONuKYc+otJBJpr/BNj+MdqZ8=
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

On Mon, Oct 27, 2008 at 6:04 PM, Tian, Kevin <kevin.tian@xxxxxxxxx> wrote:
>>From: Niraj Tolia [mailto:ntolia@xxxxxxxxx]
>>Sent: Tuesday, October 28, 2008 2:01 AM
>>On Thu, Oct 23, 2008 at 10:59 PM, Yu, Ke <ke.yu@xxxxxxxxx> wrote:
>>> After discussing with Jinsong, we got the root cause. You
>>are right, this is xen pm statistics logic issue. when the
>>coordination type is SW_ANY, we only record the first CPU
>>cpufreq change, the other 3 cores within the same dependency
>>domain is ignored, so you only see one core changes every
>>dependency domain.
>>> The attached patch fix  this issue. could you please have a
>>try? If it works in your platform, we will send out for
>>applying in upstream.
>>I just applied the patch and while xenpm might be doing the right
>>thing, I am not completely sure. For example, if I launch a single
>>VCPU VM, pin it to a core, and launch a CPU intensive task on it, ALL
>>four cores on the socket are reported to switch into P0. However, from
>>what I understand about this processor (Xeon E7330), only two of them
>>should. Like vanilla Linux, the other two should be able to operate at
>>independent voltage/frequency settings. Once again, I am not sure if
>>this is xenpm's fault or if the underlying frequency control code
>>isn't able to determine what  CPUs need to switch frequency at the
>>same time.
> Do you change any BIOS setting when comparing native Linux and
> Xen? From the xen dmesg you posted last time:

No, I did not change anything in the BIOS. However, when I run vanilla
Linux w/ cpufreqd, cpufreq-info will only list two cores being tied
together. This is with the 2.6.24-21 kernel provided with Ubuntu

# cpufreq-info
cpufrequtils 002: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to linux@xxxxxxxx, please.
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which need to switch frequency at the same time: 0 4
  hardware limits: 1.60 GHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.13 GHz, 1.87 GHz, 1.60 GHz
  available cpufreq governors: powersave, conservative, ondemand,
userspace, performance
  current policy: frequency should be within 1.60 GHz and 1.60 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 1.60 GHz.



> ...
> (XEN)   _PSD: num_entries=5 rev=0 domain=1 coord_type=253 num_processors=4
> ...
> (XEN)   _PSD: num_entries=5 rev=0 domain=2 coord_type=253 num_processors=4
> ...
> (XEN)   _PSD: num_entries=5 rev=0 domain=3 coord_type=253 num_processors=4
> ...
> You can see that BIOS reports 4 processors in a dependent domain
> with a SW_ANY coordination type. It means that any cpu within
> given dependent domain changes freq, all the rest 3 cpus change too.
> Thanks,
> Kevin

Niraj Tolia, Researcher, HP Labs

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.