This series extends the virtio-balloon stats virtqueue with new tags
for memory composition and pressure data, and adds an optional push
mode for guest-initiated stat reporting.
Patch 1 adds 11 new stat tags to the existing stats VQ.
These use the same tag/value format and require no feature negotiation.
Old hosts ignore unknown tags.
The new tags provide data needed for better balloon sizing:
a) dirty/writeback pages (more accurate reclaimable estimates)
b) workingset refault counters (balloon overshoot before PSI spikes)
c) PSI pressure stats
Also exports psi_system for module builds.
Patch 2 adds VIRTIO_BALLOON_F_STATS_PUSH.
Stats push is a new feature that lets the host configure the guest
to push stats on a timer. The host sets stats_push_interval_ms in
the balloon config space; when non-zero, the guest pushes stats at
that cadence without waiting for the host to return the buffer.
This serves two purposes:
a) latency-sensitive consumers get stats at a guaranteed cadence
b) absence of expected stats provides guest liveness detection.
STATS_PUSH requires STATS_VQ and suppresses the pull callback when
active to avoid racing on buffer submission.
Gregory Price (2):
virtio-balloon: extend stats with memory composition and pressure data
virtio-balloon: add stats push mode
drivers/virtio/virtio_balloon.c | 104 ++++++++++++++++++++++++++++
include/uapi/linux/virtio_balloon.h | 33 ++++++++-
kernel/sched/psi.c | 1 +
3 files changed, 136 insertions(+), 2 deletions(-)
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2.54.0
