Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations

Paolo Bonzini
2016-08-17T17:02:32Z

On 17/08/2016 19:01, Punit Agrawal wrote:
>> Can you explain what this is used for? In other words, why would this
>> be used instead of just running perf in the guest?
>
> As TLB maintenance operations are synchronised in hardware, they can
> impact performance beyond the guest. The operations generate traffic on
> the interconnect and depending on the implementation, they can also
> affect the remote TLB's translation bandwidth.
>
> These patches are useful on systems where the host and guest are
> controlled by different users - the guest could be running arbitrary
> software.
>
> Having the ability to monitor the usage of guest TLB invalidations in
> the host can be useful to diagnose performance issues on such systems.

Are there hardware performance counters for these operations?

Paolo