On 18.12.23 16:16, David Stevens wrote:
On Mon, Dec 18, 2023 at 6:37 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
On 14.12.23 05:13, David Stevens wrote:
On Wed, Dec 13, 2023 at 5:44 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
On 11.12.23 12:43, David Stevens wrote:
From: David Stevens <stevensd@xxxxxxxxxxxx>
Hi David,
Add a wakeup event for when the balloon is inflating or deflating.
Userspace can enable this wakeup event to prevent the system from
suspending while the balloon is being adjusted. This allows
/sys/power/wakeup_count to be used without breaking virtio_balloon's
cooperative memory management.
Can you add/share some more details
I'm working on enabling support for Linux s2Idle in our Android
virtual machine, to restrict apps from running in the background
without holding an Android partial wakelock. With the patch I recently
sent out [1], since crosvm advertises native PCI power management for
virtio devices, the Android guest can properly enter s2idle, and it
can be woken up by incoming IO. However, one of the remaining problems
is that when the host needs to reclaim memory from the guest via the
virtio-balloon, there is nothing preventing the guest from entering
s2idle before the balloon driver finishes returning memory to the
host.
Thanks for the information. So you also want to wakeup the VM when
wanting to get more memory from the VM?
Using which mechanism would that wakeup happen? Likely not the device
itself?
The wakeup would happen via the parent device's interrupt. I've sent a
new version of this patch that uses the parent device's wakeup event
instead of adding a new one.
One alternative to this approach would be to add a virtballoon_suspend
callback to abort suspend if the balloon is inflating/adjusting.
However, it seems cleaner to just prevent suspend in the first place.
Also, the PM notifier could also be used with very high priority, so the
device would respond early to PM_SUSPEND_PREPARE.
One drawback of blocking suspend via a PM notifier is that the
behavior isn't configurable by userspace, whereas wakeup events can be
enabled/disabled by userspace.
The question is if that behavior for the balloon is really worth it
being configured by user space?
--
Cheers,
David / dhildenb
