[virtio-dev] Re: [PATCH v13 4/5] mm: support reporting free page blocks

[Wei Wang <wei.w.wang@intel.com>]

On 08/04/2017 04:24 PM, Michal Hocko wrote:
>
>> For our use case, the callback just puts the reported page
>> block to the ring, then returns. If the ring is full as the host
>> is busy, then I think it should skip this one, and just return.
>> Because:
>>      A. This is an optimization feature, losing a couple of free
>>           pages to report isn't that important;
>>      B. In reality, I think it's uncommon to see this ring getting
>>          full (I didn't observe ring full in the tests), since the host
>>          (consumer) is notified to take out the page block right
>>          after it is added.
> I thought you only updated a pre allocated bitmat... Anyway, I cannot
> comment on this part much as I am not familiar with your usecase.
>   

Actually the bitmap is in the hypervisor (host). The callback puts the
(pfn,size) on a ring which is shared with the hypervisor, then the
hypervisor takes that info from the ring and updates that bitmap.


Best,
Wei

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