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

From Punit Agrawal <punit.agrawal@arm.com>
Newsgroups linux.kernel
Subject Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations
Date 2016-08-17 19:30 +0200
Message-ID <s7cP7-469-25@gated-at.bofh.it> (permalink)
References <s6K6t-1XD-3@gated-at.bofh.it> <s7bq2-32y-7@gated-at.bofh.it> <s7cvM-3X4-9@gated-at.bofh.it> <s7cvM-3X4-23@gated-at.bofh.it>
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Paolo Bonzini <pbonzini@redhat.com> writes:

> 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?

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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> kvmarm mailing list
> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

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Thread

[RFC PATCH 0/7] Add support for monitoring guest TLB operations Punit Agrawal <punit.agrawal@arm.com> - 2016-08-16 12:50 +0200
  [RFC PATCH 2/7] KVM: Track the pid of the VM process Punit Agrawal <punit.agrawal@arm.com> - 2016-08-16 12:50 +0200
  [RFC PATCH 1/7] perf/trace: Add notification for perf trace events Punit Agrawal <punit.agrawal@arm.com> - 2016-08-16 12:50 +0200
  [RFC PATCH 6/7] arm64: KVM: Handle trappable TLB instructions Punit Agrawal <punit.agrawal@arm.com> - 2016-08-16 12:50 +0200
    Re: [RFC PATCH 6/7] arm64: KVM: Handle trappable TLB instructions Will Deacon <will.deacon@arm.com> - 2016-08-19 17:20 +0200
      Re: [RFC PATCH 6/7] arm64: KVM: Handle trappable TLB instructions Punit Agrawal <punit.agrawal@arm.com> - 2016-08-24 12:50 +0200
  [RFC PATCH 3/7] KVM: arm/arm64: Register perf trace event notifier Punit Agrawal <punit.agrawal@arm.com> - 2016-08-16 12:50 +0200
  Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations Paolo Bonzini <pbonzini@redhat.com> - 2016-08-17 18:00 +0200
    Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations Punit Agrawal <punit.agrawal@arm.com> - 2016-08-17 19:10 +0200
      Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations Paolo Bonzini <pbonzini@redhat.com> - 2016-08-17 19:10 +0200
        Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations Punit Agrawal <punit.agrawal@arm.com> - 2016-08-17 19:30 +0200
          Re: [RFC PATCH 0/7] Add support for monitoring guest TLB operations Paolo Bonzini <pbonzini@redhat.com> - 2016-08-18 09:10 +0200

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