Re: [PATCH v2 2/2] virtio_balloon: replace oom notifier with shrinker

From: Tetsuo Handa
Date: Thu Aug 02 2018 - 12:03:31 EST

On 2018/08/02 19:32, Wei Wang wrote:
> On 08/01/2018 07:34 PM, Michal Hocko wrote:
>> Do you have any numbers for how does this work in practice?
> It works in this way: for example, we can set the parameter, balloon_pages_to_shrink,
> to shrink 1GB memory once shrink scan is called. Now, we have a 8GB guest, and we balloon
> out 7GB. When shrink scan is called, the balloon driver will get back 1GB memory and give
> them back to mm, then the ballooned memory becomes 6GB.

Since shrinker might be called concurrently (am I correct?), the balloon might deflate
far more than needed if it releases such much memory. If shrinker is used, releasing 256
pages might be sufficient.