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

["Niraj Tolia" <ntolia@xxxxxxxxx>]

On Wed, Oct 22, 2008 at 1:16 AM, Yu, Ke <ke.yu@xxxxxxxxx> wrote:
> You can simply add xen grub option "cpufreq=xen cpuidle" to enable C and P 
> state, like the following:
> kernel /boot/xen.gz dom0_mem=256M console=com1 cpufreq=xen cpuidle.
>

Hi Ke,

This seems to "work" but xenpm doesn't seem to be giving me the right
data. On a completely idle system, the residency time of state C1 is
0ms. xentrace does report a large number of transitions though but
they seem to be in rapid succession. Is this correct?

CPU4  320429115477 (+24006897)  cpu_idle_exit   [ C1 -> C0 ]
CPU4  320429118141 (+    2664)  cpu_idle_entry  [ C0 -> C1 ]
CPU4  320437500021 (+ 8381880)  cpu_idle_exit   [ C1 -> C0 ]
CPU4  320437505493 (+    5472)  cpu_idle_entry  [ C0 -> C1 ]
CPU4  320453123229 (+15617736)  cpu_idle_exit   [ C1 -> C0 ]
CPU4  320453125992 (+    2763)  cpu_idle_entry  [ C0 -> C1 ]
CPU4  320477132295 (+24006303)  cpu_idle_exit   [ C1 -> C0 ]
CPU4  320477134968 (+    2673)  cpu_idle_entry  [ C0 -> C1 ]


Second, when I look at the P-state output (shown below), xenpm shows
that the lowest P-state is only set on the first socket (this is a
quad-core, quad-socket system). However, I have a feeling that this
might be a problem with displaying the data rather than the underlying
logic. Any ideas?

# xenpm | grep '*'
*P3                  : freq       [1599 MHz]
*P3                  : freq       [1599 MHz]
*P3                  : freq       [1599 MHz]
*P3                  : freq       [1599 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]
*P0                  : freq       [2398 MHz]

Cheers,
Niraj

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