Re: [Xen-devel] [PATCH] common/vm_event: Initialize vm_event lists on domain creation

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 06/27/2017 09:21 AM, Jan Beulich wrote:
>>>> Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 06/26/17 5:11 PM >>>
>> There is also a difference in timing; vm_event_init_domain() is called
>> when vm_event is started on the domain, not when the domain is
>> constructed.  IMO, the two should happen at the same time to be
>> consistent.  I'm not fussed at which point, as it would be fine (in
>> principle) for d->vm_event to be NULL in most cases.
> 
> I very much support that last aspect - there's shouldn't be any memory
> allocated here if the domain isn't going to make use of VM events.

Unfortunately it's not as simple as that.

While I didn't write that code, it would seem that on domain creation
that data is being allocated because it holds information about 3
different vm_event subsystems - monitor, paging, and memshare.

vm_event_init_domain() is then not being called when vm_event generally
is started on the domain, but when a specific vm_event part is being
initialized (monitor usually, but could be paging, etc.).


Thanks,
Razvan

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