Re: [Xen-devel] kernel bootup slow issue on ovm3.1.1

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.08.12 at 11:48, "zhenzhong.duan" <zhenzhong.duan@xxxxxxxxxx> wrote:
> ä 2012-08-07 16:37, Jan Beulich åé:
>>>>> On 07.08.12 at 09:22, "zhenzhong.duan"<zhenzhong.duan@xxxxxxxxxx>  wrote:
>> Next, if you already spotted where the spinning occurs, you
>> should also be able to tell what's going on at the other side, i.e.
>> why the event that is being waited for isn't occurring for this
>> long a time. Since there's a number of open coded spin loops
>> here, knowing exactly which one each CPU is sitting in (and
>> which ones might not be in any) is the fundamental information
>> needed.
>>
>>  From what you're telling us so far, I'd rather suspect a kernel
>> problem, not a hypervisor one here.
> Per my finding, most of vcpus spin at set_atomicity_lock.

Then you need to determine what the current owner of the
lock is doing.

> Some spin at stop_machine after finish their job.

And here you'd need to find out what they're waiting for,
and what those CPUs are doing.

> Only one vcpu is calling generic_set_all.
> I'm not sure if the vcpu calling generic_set_all don't have higher 
> priority and maybe preempt by other vcpus and dom0 frequently.
> This waste much time.

There's not that much being done in generic_set_all(), so the
code should finish reasonably quickly. Are you perhaps having
more vCPU-s in the guest than pCPU-s they can run on? Does
your hardware support Pause-Loop-Exiting (or the AMD
equivalent, don't recall their term right now)?

Jan

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