[Xen-devel] some thoughts about merlot{0|1} issues [was: Re: [xen-unstable test] 102522: tolerable FAIL - PUSHED]

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 24.11.16 at 16:14, <dario.faggioli@xxxxxxxxxx> wrote:
> When dumping ACPI C states, here's how things look like for _all_ CPUs:
> Nov 23 13:13:00.382134 (XEN) ==cpu3==
> Nov 23 13:13:00.382157 (XEN) active state:            C-1
> Nov 23 13:13:00.390096 (XEN) max_cstate:              C7
> Nov 23 13:13:00.390125 (XEN) states:
> Nov 23 13:13:00.390148 (XEN)     C1:  type[C1] latency[000] usage[00000000] 
> method[ HALT] duration[0]
> Nov 23 13:13:00.398055 (XEN)     C0:  usage[00000000] duration[4229118701384]
> Nov 23 13:13:00.398090 (XEN) PC2[0] PC3[0] PC6[0] PC7[0]
> Nov 23 13:13:00.406088 (XEN) CC3[0] CC6[0] CC7[0]
> 
> And I checked other runs, and it's the same everywhere.
> 
> I remember that Jan suggested trying to pass max_cstate=1 to Xen at
> boot. I was about to ask Ian to do that for this host, but it looks
> like we're using only C0 and C1 already anyway.

This indeed looks surprising for a half way modern system - is the
BIOS perhaps limiting C-states (maybe instructed to via BIOS setup)?

Jan


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