[PATCH RFC] virtio_balloon: conservative balloon page shrinking

Wang, Wei W
2020-02-10T03:13:21Z

On Saturday, February 8, 2020 8:33 PM, Tetsuo Handa
wrote:
>
> Is this NUMA aware? Can "node-A's NR_FILE_PAGES is already 0 and
> node-B's NR_FILE_PAGES is not 0, but allocation request which triggered
this
> shrinker wants to allocate from only node-B" happen?

No, it's a global counter.

>Can some thread keep
> this shrinker defunctional by keep increasing NR_FILE_PAGES?

Yes. Actually it's our intention - as long as there are pagecache pages,
balloon pages are avoided to be reclaimed.


>
> Is this patch from "Re: Balloon pressuring page cache" thread? I
hope that
> the guest could start reclaiming memory based on host's request (like
OOM
> notifier chain) which is issued when host thinks that host is getting close
to
> OOM and thus guests should start returning their unused memory to host.
> Maybe "periodically (e.g. 5 minutes)" in addition to "upon
close to OOM
> condition" is also possible.

That's about the host usages. The host side management software decides when
to issue a request to balloon (either periodically or event driven), I think
there isn't anything we need to do in the balloon driver here.

Best,
Wei