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

From: Wei Wang
Date: Fri Aug 04 2017 - 04:52:48 EST

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.
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.