Hi T.J,
This topic proposal would be to present and discuss multiple MM
features to improve host memory overcommit while running VMs. There
are two general cases:
1. The host and its guests operate independently,
2. The host and its guests cooperate by techniques like ballooning.
In the first case, we would discuss some new techniques, e.g., fast
access bit harvesting in the KVM MMU, and some difficulties, e.g.,
double zswapping.
In the second case, we would like to discuss a novel working set size
(WSS) notifier framework and some improvements to the ballooning
policy. The WSS notifier, when available, can report WSS to its
listeners. VM Memory Overcommit is one of its use cases: the
virtio-balloon driver can register for WSS notifications and relay WSS
to the host. The host can leverage the WSS notifications and improve
the ballooning policy.
I am interested in this discussion. Have few questions below:
- What kind/frequency of data we expect WSS would relay to the host in
good and worst case?
- Thoughts already considered about the overhead VM will have based on
WSS relay data to the host and host taking action on the data?
-- One thing iirc from the free page hinting design experiments is
preventing guest and host acting simultaneously (e.g for free) on
same page (pfn) and also reducing the overhead of sending data from
guest to host by sending the highest possible page order.
Maybe some of these or other similar techniques are already considered.
Thanks,
Pankaj
This topic would be of interest to a wide range of audience, e.g.,
phones, laptops and servers.
Co-presented with Yuanchu Xie.
Thanks,
-T.J.
