Re: [Xen-devel] [PATCH 2/2] xen: spread page scrubbing across all idle CPU

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.06.14 at 04:51, <bob.liu@xxxxxxxxxx> wrote:
> On 06/10/2014 10:12 PM, Jan Beulich wrote:
>>>>> On 10.06.14 at 14:18, <lliubbo@xxxxxxxxx> wrote:
>>> +    if( is_tasklet )
>>> +        tasklet_schedule_on_cpu(&global_scrub_tasklet, cpu);
>> 
>> So you re-schedule this tasklet immediately - while this may be
>> acceptable inside the hypervisor, did you consider the effect this
>> will have on the guest (normally Dom0)? Its respective vCPU won't
>> get run _at all_ until you're done scrubbing.
>> 
> 
> Yes, that's a problem. I don't have any better idea right now.
> 
> What I'm trying is doing the scrubbing on current CPU as well as on all
> idle vcpus in parallel.
> I also considered your suggestion about doing the scrubbing in the
> background as well as on the allocation path. But I think it's more
> unacceptable for users to get blocked randomly for a uncertain time when
> allocating a large mount of memory.
> That's why I still chose the sync way that once 'xl destroy' return all
> memory are scrubbed.

But I hope you realize that in the current shape, with the shortcomings
pointed out un-addressed, there's no way for this to go in.

Jan


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