On 1/19/26 16:42, Jack Thomson wrote:
From: Jack Thomson <[email protected]>
This RFC patch adds a new virtio feature for the virtio-balloon driver
during free page hinting, which will wait on device ack before
committing the range to the free_page_list. The reason for the change is
it allows the device to modify this range without it being reclaimed
from the free_page_list before the ack is sent. As expected, testing
shows this adds overhead to the hinting run duration, increasing it by
~30% with our Firecracker setup. Currently free page hinting is used
mainly for live migration, but this would open it up for a new use-case.
We would like to leverage this with MADV_DONTNEED to reduce RSS of a
guest. We'd like to use hinting because of the flexibility of control it
brings compared to reporting, allowing memory to be reclaimed in
deterministic periods.
Can you elaborate in more detail why you don't simply use reporting,
like QEMU?
Could you instead see optimizations being done to reporting that could
make it fly for your use case?
Hinting is a rather special case thing only used for reducing VM
migration time in QEMU AFAIR.
--
Cheers
David
