From: Andrew Murray <andrew.murray@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Julien Thierry <julien.thierry@arm.com>,
suzuki.poulose@arm.com,
Christoffer Dall <christoffer.dall@arm.com>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH v2 0/5] KVM: arm/arm64: add support for chained counters
Date: Mon, 18 Feb 2019 12:10:26 +0000 [thread overview]
Message-ID: <20190218121026.GI54124@e119886-lin.cambridge.arm.com> (raw)
In-Reply-To: <20190218085217.4c4ff56f@why.wild-wind.fr.eu.org>
On Mon, Feb 18, 2019 at 08:52:17AM +0000, Marc Zyngier wrote:
> On Mon, 4 Feb 2019 16:53:33 +0000
> Andrew Murray <andrew.murray@arm.com> wrote:
>
> > ARMv8 provides support for chained PMU counters, where an event type
> > of 0x001E is set for odd-numbered counters, the event counter will
> > increment by one for each overflow of the preceding even-numbered
> > counter. Let's emulate this in KVM by creating a 64 bit perf counter
> > when a user chains two emulated counters together.
> >
> > Testing has been performed by hard-coding hwc->sample_period in
> > __hw_perf_event_init (arm_pmu.c) to a small value, this results in
> > regular overflows (for non sampling events). The following command
> > was then used to measure chained and non-chained instruction cycles:
> >
> > perf stat -e armv8_pmuv3/long=1,inst_retired/u \
> > -e armv8_pmuv3/long=0,inst_retired/u dd if=/dev/zero bs=1M \
> > count=10 | gzip > /dev/null
> >
> > The reported values were identical (and for non-chained was in the
> > same ballpark when running on a kernel without this patchset). Debug
> > was added to verify that the guest received overflow interrupts for
> > the chain counter.
>
> Hi Andrew,
>
> We're getting quite close to the merge window, and I need to wrap up the
> pull request pretty soon. If you want this to make it into 5.1, you'll
> have to respin it pretty quickly (right now, basically...), addressing
> the comments Suzuki and Julien raised.
>
Thanks for the prompt, I'll send this out very shortly.
Thanks,
Andrew Murray
> Thanks,
>
> M.
> --
> Without deviation from the norm, progress is not possible.
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prev parent reply other threads:[~2019-02-18 12:10 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-04 16:53 [PATCH v2 0/5] KVM: arm/arm64: add support for chained counters Andrew Murray
2019-02-04 16:53 ` [PATCH v2 1/5] KVM: arm/arm64: rename kvm_pmu_{enable/disable}_counter functions Andrew Murray
2019-02-05 12:21 ` Julien Thierry
2019-02-11 17:23 ` Suzuki K Poulose
2019-02-04 16:53 ` [PATCH v2 2/5] KVM: arm/arm64: extract duplicated code to own function Andrew Murray
2019-02-04 16:53 ` [PATCH v2 3/5] KVM: arm/arm64: re-create event when setting counter value Andrew Murray
2019-02-05 12:21 ` Julien Thierry
2019-02-05 12:27 ` Andrew Murray
2019-02-13 14:28 ` Suzuki K Poulose
2019-02-18 9:39 ` Andrew Murray
2019-02-04 16:53 ` [PATCH v2 4/5] KVM: arm/arm64: lazily create perf events on enable Andrew Murray
2019-02-14 11:36 ` Suzuki K Poulose
2019-02-18 9:57 ` Andrew Murray
2019-02-04 16:53 ` [PATCH v2 5/5] KVM: arm/arm64: support chained PMU counters Andrew Murray
2019-02-05 14:33 ` Julien Thierry
2019-02-14 11:42 ` Suzuki K Poulose
2019-02-18 12:03 ` Andrew Murray
2019-02-18 14:02 ` Marc Zyngier
2019-02-18 10:11 ` Andrew Murray
2019-02-18 8:52 ` [PATCH v2 0/5] KVM: arm/arm64: add support for chained counters Marc Zyngier
2019-02-18 12:10 ` Andrew Murray [this message]
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