Paolo Bonzini [off-list ref] writes:

On 17/08/2016 19:01, Punit Agrawal wrote:

quoted

quoted

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?

That would have been ideal! There are PMU events defined for TLB
accesses and refills but unhelpfully none of them track maintenance
operations.

Paolo
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