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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