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From: Robin Murphy <robin.murphy@arm.com>
To: Mark Rutland <mark.rutland@arm.com>,
	linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com, will@kernel.org,
	kvmarm@lists.cs.columbia.edu, maz@kernel.org
Subject: Re: [PATCHv6 0/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters
Date: Tue, 10 Mar 2020 17:28:15 +0000	[thread overview]
Message-ID: <2713672f-bd82-ba8d-5fae-777ef5e754eb@arm.com> (raw)
In-Reply-To: <20200303190742.GD7649@lakrids.cambridge.arm.com>

On 03/03/2020 7:07 pm, Mark Rutland wrote:
> On Mon, Mar 02, 2020 at 06:17:49PM +0000, Mark Rutland wrote:
>> This is a respin of Andrew Murray's series to enable support for 64-bit
>> counters as introduced in ARMv8.5.
>>
>> I've given this a spin on (ARMv8.2) hardware, to test that there are no
>> regressions, but I have not had the chance to test in an ARMv8.5 model (which I
>> beleive Andrew had previously tested).
> 
> Bad news; this is broken. :(
> 
> While perf-stat works as expected, perf-record doesn't get samples for
> any of the programmable counters.
> 
> In ARMv8.4 mode I can do:
> 
> | / # perf record -a -c 1 -e armv8_pmuv3/inst_retired/ true
> | [ perf record: Woken up 1 times to write data ]
> | [ perf record: Captured and wrote 0.023 MB perf.data (367 samples) ]
> | / # perf record -a -c 1 -e armv8_pmuv3/inst_retired,long/ true
> | [ perf record: Woken up 1 times to write data ]
> | [ perf record: Captured and wrote 0.022 MB perf.data (353 samples) ]
> 
> ... so regular 32-bit and chained events work correctly.
> 
> But in ARMv8.5 mode I get no samples in either case:
> 
> | / # perf record -a -c 1 -e armv8_pmuv3/inst_retired/ true
> | [ perf record: Woken up 1 times to write data ]
> | [ perf record: Captured and wrote 0.008 MB perf.data ]
> | / # perf report | grep samples
> | Error:
> | The perf.data file has no samples!
> | / # perf record -a -c 1 -e armv8_pmuv3/inst_retired,long/ true
> | [ perf record: Woken up 1 times to write data ]
> | [ perf record: Captured and wrote 0.008 MB perf.data ]
> | / # perf report | grep samples
> | Error:
> | The perf.data file has no samples!
> 
> I'll have to trace the driver to see what's going on. I suspect we've
> missed some bias handling, but it's possible that this is a model bug.

For the record, further evidence has indeed pointed to there being a bug 
in the model's implementation of ARMv8.5-PMU. It's been raised with the 
models team, so we'll have wait and see what they say...

Robin.
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  reply	other threads:[~2020-03-10 17:28 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-02 18:17 [PATCHv6 0/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters Mark Rutland
2020-03-02 18:17 ` [PATCHv6 1/3] arm64: cpufeature: Extract capped perfmon fields Mark Rutland
2020-03-02 18:17 ` [PATCHv6 2/3] KVM: arm64: limit PMU version to PMUv3 for ARMv8.1 Mark Rutland
2020-03-02 18:17 ` [PATCHv6 3/3] arm64: perf: Add support for ARMv8.5-PMU 64-bit counters Mark Rutland
2020-03-03 19:07 ` [PATCHv6 0/3] " Mark Rutland
2020-03-10 17:28   ` Robin Murphy [this message]
2020-03-17 23:14 ` Will Deacon
2020-03-18 10:51   ` Mark Rutland

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