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Subject: Re: [PATCH 0/2] powerpc/kvm: Enable running guests on RT Linux
From: Scott Wood <scottwood@freescale.com>
To: Purcareata Bogdan <b43198@freescale.com>
Date: Thu, 9 Apr 2015 18:53:31 -0500
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Cc: linux-rt-users@vger.kernel.org,
 Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
 Alexander Graf <agraf@suse.de>, linux-kernel@vger.kernel.org,
 Bogdan Purcareata <bogdan.purcareata@freescale.com>,
 mihai.caraman@freescale.com, Paolo Bonzini <pbonzini@redhat.com>,
 Thomas Gleixner <tglx@linutronix.de>, linuxppc-dev@lists.ozlabs.org
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On Thu, 2015-04-09 at 10:44 +0300, Purcareata Bogdan wrote:
> So at this point I was getting kinda frustrated so I decided to measure
> the time spend in kvm_mpic_write and kvm_mpic_read. I assumed these were
> the main entry points in the in-kernel MPIC and were basically executed
> while holding the spinlock. The scenario was the same - 24 VCPUs guest,
> with 24 virtio+vhost interfaces, only this time I ran 24 ping flood
> threads to another board instead of netperf. I assumed this would impose
> a heavier stress.
> 
> The latencies look pretty ok, around 1-2 us on average, with the max
> shown below:
> 
> .kvm_mpic_read	14.560
> .kvm_mpic_write	12.608
> 
> Those are also microseconds. This was run for about 15 mins.

What about other entry points such as kvm_set_msi() and
kvmppc_mpic_set_epr()?

-Scott