On 10/03/21 18:31, Marc Zyngier wrote:
Maintaining VM-global counters would require an atomic instruction and
would suffer lots of cacheline bouncing even on architectures that
have relaxed atomic memory operations.
Which is why we have per-cpu counters already. Making use of them
doesn't seem that outlandish.
But you wouldn't be able to guarantee consistency anyway, would you?
You *could* copy N*M counters to userspace, but there's no guarantee
that they are consistent, neither within a single vCPU nor within a
single counter.
Speed/efficiency of retrieving statistics is important, but let's keep
in mind that the baseline for comparison is hundreds of syscalls and
filesystem lookups.
Having that baseline in the cover letter would be a good start, as
well as an indication of the frequency this is used at.
Can't disagree, especially on the latter which I have no idea about.
Paolo
