[pve-devel] [PATCH qemu-server] fix #6207: vm status: cache last disk read/write values

[Thomas Lamprecht]

Am 22.09.25 um 12:18 schrieb Fiona Ebner:
> If disk read/write cannot be queried because of QMP timeout, they
> should not be reported as 0, but the last value should be re-used.
> Otherwise, the difference between that reported 0 and the next value,
> when the stats are queried successfully, will show up as a huge spike
> in the RRD graphs.

Fine with the idea in general, but this is effectively relevant for
the pvestatd only though?

As of now we would also cache in the API daemon, without every using
this. Might not be _that_ much, so not really a problem of the amount,
but feels a bit wrong to me w.r.t. "code place".

Has pvestatd the necessary info, directly on indirectly through the
existence of some other vmstatus properties, to derive when it can
safely reuse the previous value?

Or maybe we could make this caching opt-in through some module flag
that only pvestatd sets? But not really thought that through, so
please take this with a grain of salt.

btw. what about QMP being "stuck" for a prolonged time, should we
stop using the previous value after a few times (or duration)?