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Re: Null scheduler and vwfi native problem

On 29.01.21 09:08, Anders Törnqvist wrote:
On 1/26/21 11:31 PM, Dario Faggioli wrote:
On Tue, 2021-01-26 at 18:03 +0100, Anders Törnqvist wrote:
On 1/25/21 5:11 PM, Dario Faggioli wrote:
On Fri, 2021-01-22 at 14:26 +0000, Julien Grall wrote:
Hi Anders,

On 22/01/2021 08:06, Anders Törnqvist wrote:
On 1/22/21 12:35 AM, Dario Faggioli wrote:
On Thu, 2021-01-21 at 19:40 +0000, Julien Grall wrote:
- booting with "sched=null vwfi=native" but not doing the IRQ
passthrough that you mentioned above
"xl destroy" gives
(XEN) End of domain_destroy function

Then a "xl create" says nothing but the domain has not started
"xl list" look like this for the domain:
mydomu                                   2   512     1 ------
This is odd. I would have expected ``xl create`` to fail if
went wrong with the domain creation.

So, Anders, would it be possible to issue a:

# xl debug-keys r
# xl dmesg

And send it to us ?

Ideally, you'd do it:
   - with Julien's patch (the one he sent the other day, and that
     have already given a try to) applied
   - while you are in the state above, i.e., after having tried to
     destroy a domain and failing
   - and maybe again after having tried to start a new domain
Here are some logs.

Great, thanks a lot!

The system is booted as before with the patch and the domu config
not have the IRQs.


# xl list
Name                                        ID   Mem VCPUs State
Domain-0                                     0  3000     5 r-----
mydomu                                       1   511     1 r-----

# xl debug-keys r
(XEN) sched_smt_power_savings: disabled
(XEN) NOW=191793008000
(XEN) Online Cpus: 0-5
(XEN) Cpupool 0:
(XEN) Cpus: 0-5
(XEN) Scheduler: null Scheduler (null)
(XEN)     cpus_free =
(XEN) Domain info:
(XEN)     Domain: 0
(XEN)       1: [0.0] pcpu=0
(XEN)       2: [0.1] pcpu=1
(XEN)       3: [0.2] pcpu=2
(XEN)       4: [0.3] pcpu=3
(XEN)       5: [0.4] pcpu=4
(XEN)     Domain: 1
(XEN)       6: [1.0] pcpu=5
(XEN) Waitqueue:

So far, so good. All vCPUs are running on their assigned pCPU, and
there is no vCPU wanting to run but not having a vCPU where to do so.

(XEN) Command line: console=dtuart dtuart=/serial@5a060000
dom0_mem=3000M dom0_max_vcpus=5 hmp-unsafe=true dom0_vcpus_pin
sched=null vwfi=native

Oh, just as a side note (and most likely unrelated to the problem we're
discussing), you should be able to get rid of dom0_vcpus_pin.

The NULL scheduler will do something similar to what that option itself
does anyway. And with the benefit that, if you want, you can actually
change to what pCPUs the dom0's vCPU are pinned. While, if you use
dom0_vcpus_pin, you can't.

So it using it has only downsides (and that's true in general, if you
ask me, but particularly so if using NULL).
Thanks for the feedback.
I removed dom0_vcpus_pin. And, as you said, it seems to be unrelated to the problem we're discussing. The system still behaves the same.

When the dom0_vcpus_pin is removed. xl vcpu-list looks like this:

Name                                ID  VCPU   CPU State Time(s) Affinity (Hard / Soft)
Domain-0                             0     0    0   r--      29.4 all / all
Domain-0                             0     1    1   r--      28.7 all / all
Domain-0                             0     2    2   r--      28.7 all / all
Domain-0                             0     3    3   r--      28.6 all / all
Domain-0                             0     4    4   r--      28.6 all / all
mydomu                              1     0    5   r--      21.6 5 / all

From this listing (with "all" as hard affinity for dom0) one might read it like dom0 is not pinned with hard affinity to any specific pCPUs at all but mudomu is pinned to pCPU 5. Will the dom0_max_vcpus=5 in this case guarantee that dom0 only will run on pCPU 0-4 so that mydomu always will have pCPU 5 for itself only?


What if I would like mydomu to be th only domain that uses pCPU 2?

Setup a cpupool with that pcpu assigned to it and put your domain into
that cpupool.


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