Re: [PATCH 0/4] paravirt clock patches

Gerd Hoffmann
2008-05-05T07:47:59Z

Marcelo Tosatti wrote:
> On Thu, Apr 24, 2008 at 10:37:04AM +0200, Gerd Hoffmann wrote:
>> Hi folks,
>>
>> My first attempt to send out a patch series with git ...
>>
>> The patches fix the kvm paravirt clocksource code to be compatible with
>> xen and they also factor out some code which can be shared into a
>> separate source files used by both kvm and xen.
>
> The issue with SMP guests is still present. Booting with "nohz=off" resolves it.
>
> Same symptoms as before, apic_timer_fn for one of the vcpu's is ticking way slower
> than the remaining ones:
>
> [root@localhost ~]# cat /proc/timer_stats | grep apic
> 391, 4125 qemu-system-x86 apic_mmio_write (apic_timer_fn)
> 2103, 4126 qemu-system-x86 apic_mmio_write (apic_timer_fn)
> 1896, 4127 qemu-system-x86 apic_mmio_write (apic_timer_fn)
> 1857, 4128 qemu-system-x86 apic_mmio_write (apic_timer_fn)

What userspace version is this? With iothread support? Or older one
where the vcpu0 thread also handles all the I/O? Is 4x neeed to
reproduce or do you see it with 2x too? What host?

A quick test with xenner (which has a separate I/O thread) didn't show
anything unusual. Going investigate ...

cheers,
Gerd

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