Re: [Xen-devel] [PATCH v3 4/9] mm: Scrub memory from idle loop

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 05/05/2017 10:14 AM, Jan Beulich wrote:
>>>> On 05.05.17 at 16:10, <JBeulich@xxxxxxxx> wrote:
>>>>> On 05.05.17 at 15:42, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>>>>> Otoh there's not much to scrub yet until Dom0 had all its memory
>>>>>> allocated, and we know which pages truly remain free (wanting
>>>>>> what is currently the boot time scrubbing done on them). But that
>>>>>> point in time may still be earlier than when we switch to
>>>>>> SYS_STATE_active.
>>>> IOW I think boot scrubbing could be kicked off as soon as Dom0
>>>> had the bulk of its memory allocated.
>>> Since we only are trying to avoid mapcache vcpu override can't we just
>>> scrub whenever override is NULL (per-cpu or not)?
>> But how do you know? The variable should remain static in
>> domain_page.c, so I think we'd instead need a notification to
>> the scrubber when it gets set back to NULL.

Why not just have in domain_page.c

bool mapcache_override() {return override != NULL;}

(or appropriate per-cpu variant)?

> And of course if the override variable was per-CPU, you wouldn't
> have a need to know, as you wouldn't try scrubbing on the CPU
> doing the Dom0 setup.

Actually, won't (override != current) do the trick?

-boris



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