Re: [RFC PATCH 2/2] virtio-balloon: add stats push mode

["David Hildenbrand (Arm)" <david@kernel.org>]

On 6/16/26 16:44, Gregory Price wrote:
> On Tue, Jun 16, 2026 at 04:32:46PM +0200, David Hildenbrand (Arm) wrote:
>> On 6/16/26 15:57, Gregory Price wrote:
>>>
>>> Definitely an RFC here because I'm not sure if I was missing something
>>> that might help me solve the problem.
>>
>> Well, in QEMU we just run a timer internally that does the polling.
>>
>> Then, upper layers in the stack can ask QEMU for the latest stats.
>>
>> There, you just get the stats along with a "last-update" timestamp.
>>
> 
> That makes sense, although don't you just push the blocking operation
> into yet another thread on the host?

I think timers are run from the QEMU main thread, so no separate thread just for
the timer.

And IIRC, there will be no blocking. At least if I understand your concern
correctly.

balloon_stats_poll_cb() will do a virtqueue_push()+virtio_notify(), which will
notify the device. The main thread will continue afterwards doing what a main
thread usually does.

A VCPU will process the request in the VM and send it back + notify the device.

-- 
Cheers,

David