On Wed, Mar 10, 2021 at 11:44 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > 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 > Marc, Paolo, thanks for the comments. I will add some more information in the cover letter. Thanks, Jing
