Re: [PATCH] perf tests: Add auto counter reload (ACR) sampling test

Mi, Dapeng
2026-04-16T03:25:55Z

On 4/16/2026 11:17 AM, Ian Rogers wrote:
> On Wed, Apr 15, 2026 at 8:06 PM Mi, Dapeng <dapeng1.mi@linux.intel.com> wrote:
>>
>> On 4/16/2026 1:13 AM, Ian Rogers wrote:
>>> On Wed, Apr 15, 2026 at 2:19 AM Mi, Dapeng <dapeng1.mi@linux.intel.com> wrote:
>>>> On 4/13/2026 9:30 AM, Ian Rogers wrote:
>>>>> On Sun, Apr 12, 2026 at 6:14 PM Dapeng Mi <dapeng1.mi@linux.intel.com> wrote:
>>>>>> Add auto counter reload sampling test to verify that the intended event
>>>>>> records can be captured and the self-reloaded events won't generate any
>>>>>> records.
>>>>>>
>>>>>> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
>>>>>> ---
>>>>>> tools/perf/tests/shell/record.sh | 42 ++++++++++++++++++++++++++++++++
>>>>>> 1 file changed, 42 insertions(+)
>>>>>>
>>>>>> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
>>>>>> index 7cb81cf3444a..1068843282f5 100755
>>>>>> --- a/tools/perf/tests/shell/record.sh
>>>>>> +++ b/tools/perf/tests/shell/record.sh
>>>>>> @@ -402,6 +402,47 @@ test_callgraph() {
>>>>>> echo "Callgraph test [Success]"
>>>>>> }
>>>>>>
>>>>>> +test_acr_sampling() {
>>>>>> + events="{instructions/period=20000,acr_mask=0x2/u,cycles/period=40000,acr_mask=0x3/u}"
>>>>>> + pebs_events="{instructions/period=20000,acr_mask=0x2/pu,cycles/period=40000,acr_mask=0x3/u}"
>>>>>> + echo "Auto counter reload sampling test"
>>>>>> + if ! perf record -o "${perfdata}" -e "${events}" ${testprog} 2> /dev/null
>>>>>> + then
>>>>>> + echo "Auto counter reload sampling [Skipped not supported]"
>>>>>> + return
>>>>>> + fi
>>>>>> + if ! perf script -i "${perfdata}" | grep -q "period=20000,acr_mask=0x2"
>>>>>> + then
>>>>>> + echo "Auto counter reload sampling [Failed missing instructions event]"
>>>>>> + err=1
>>>>>> + return
>>>>>> + fi
>>>>>> + if perf script -i "${perfdata}" | grep -q "period=40000,acr_mask=0x3"
>>>>>> + then
>>>>>> + echo "Auto counter reload sampling [Failed cycles event shouldn't be sampled]"
>>>>>> + err=1
>>>>>> + return
>>>>>> + fi
>>>>>> + if ! perf record -o "${perfdata}" -e "${pebs_events}" ${testprog} 2> /dev/null
>>>>>> + then
>>>>>> + echo "Auto counter reload PEBS sampling [Skipped not supported]"
>>>>>> + return
>>>>>> + fi
>>>>>> + if ! perf script -i "${perfdata}" | grep -q "period=20000,acr_mask=0x2"
>>>>>> + then
>>>>>> + echo "Auto counter reload PEBS sampling [Failed missing instructions event]"
>>>>>> + err=1
>>>>>> + return
>>>>>> + fi
>>>>>> + if perf script -i "${perfdata}" | grep -q "period=40000,acr_mask=0x3"
>>>>>> + then
>>>>>> + echo "Auto counter reload PEBS sampling [Failed cycles event shouldn't be sampled]"
>>>>>> + err=1
>>>>>> + return
>>>>>> + fi
>>>>>> + echo "Auto counter reload sampling [Success]"
>>>>> Thanks Dapeng! Could we also test ratio-to-prev as well as just the
>>>>> plain acr_mask?
>>>> Ian, it could be hard to validate ratio-to-prev option in this test. On
>>>> platforms which don't support ACR, perf would automatically fallback the
>>>> ACR sampling to normal sampling, this would lead to false positives on
>>>> checking the existence of records from cycles event. I didn't find a good
>>>> way to figure out this fallback.
>>>>
>>>> Since we already have independent test case to validate the ratio_to_prev
>>>> parsing. It may be unnecessary to add ratio-to-prev validation in this ACR
>>>> test.
>>> So the ratio_to_prev test covers parsing the ratio-to-prev option (it
>>> only has `perf record` commands) and ensures it is acted upon, but it
>>> doesn't check the option's functional behavior - what the output is.
>>> This test makes sure the acr_mask option is functional and so would be
>>> complemented by ratio-to-prev testing somethig like:
>>> ```
>>> rtp_events="{instructions,cycles/period=40000,ratio-to-prev=0.5/u}"
>>>
>>> # Test ratio-to-prev
>>> if ! perf record -o "${perfdata}" -e "${rtp_events}" ${testprog} 2> /dev/null
>>> then
>>> echo "Auto counter reload ratio-to-prev sampling [Failed record
>>> ratio-to-prev]"
>>> err=1
>>> return
>>> fi
>>> if ! perf script -i "${perfdata}" | grep -q "instructions"
>>> then
>>> echo "Auto counter reload ratio-to-prev sampling [Failed missing
>>> instructions event]"
>>> err=1
>>> return
>>> fi
>>> if perf script -i "${perfdata}" | grep -q "cycles"
>>> then
>>> echo "Auto counter reload ratio-to-prev sampling [Failed cycles
>>> event shouldn't be sampled]"
>>> err=1
>>> return
>>> fi
>>> ```
>>> The first thing your test does is to make sure the acr_mask is
>>> supported, so I'm not sure how the fall back can happen?
>>> We could additionally check for
>>> `/sys/bus/event_source/devices/cpu*/format/acr_mask`.
>> Yes, that's initially what I intended to do, but it would cause false
>> positives on some hybrid platform, like PTL which only supports ACR on E-core.
>>
>> ```
>>
>> $ grep . /sys/bus/event_source/devices/cpu_core/format/*
>> /sys/bus/event_source/devices/cpu_core/format/cmask:config:24-31
>> /sys/bus/event_source/devices/cpu_core/format/edge:config:18
>> /sys/bus/event_source/devices/cpu_core/format/eq:config:36
>> /sys/bus/event_source/devices/cpu_core/format/event:config:0-7
>> /sys/bus/event_source/devices/cpu_core/format/frontend:config1:0-23
>> /sys/bus/event_source/devices/cpu_core/format/inv:config:23
>> /sys/bus/event_source/devices/cpu_core/format/ldlat:config1:0-15
>> /sys/bus/event_source/devices/cpu_core/format/metrics_clear:config1:0
>> /sys/bus/event_source/devices/cpu_core/format/offcore_rsp:config1:0-63
>> /sys/bus/event_source/devices/cpu_core/format/pc:config:19
>> /sys/bus/event_source/devices/cpu_core/format/umask:config:8-15,40-47
>>
>> $ grep . /sys/bus/event_source/devices/cpu_atom/format/*
>> /sys/bus/event_source/devices/cpu_atom/format/acr_mask:config2:0-63
>> /sys/bus/event_source/devices/cpu_atom/format/cmask:config:24-31
>> /sys/bus/event_source/devices/cpu_atom/format/edge:config:18
>> /sys/bus/event_source/devices/cpu_atom/format/eq:config:36
>> /sys/bus/event_source/devices/cpu_atom/format/event:config:0-7
>> /sys/bus/event_source/devices/cpu_atom/format/inv:config:23
>> /sys/bus/event_source/devices/cpu_atom/format/ldlat:config1:0-15
>> /sys/bus/event_source/devices/cpu_atom/format/offcore_rsp:config1:0-63
>> /sys/bus/event_source/devices/cpu_atom/format/pc:config:19
>> /sys/bus/event_source/devices/cpu_atom/format/snoop_rsp:config1:0-63
>> /sys/bus/event_source/devices/cpu_atom/format/umask:config:8-15,40-47
>>
>> ```
>>
>> So strictly speaking, we need to check if it's a hybrid platform first and
>> then check if the exact P-core/E-core supports ACR, then run the above ACR
>> tests. It seems a little bit over-complicated and I'm not sure if it's
>> accepted to add so much Intel specific check in the record.sh.
>>
>> How's your idea on this? Thanks.
> Potentially auto counter reload and ratio to prev are generic
> concepts, it just happens that we only have Intel e-core
> implementations :-) Matching against cpu* already misses ARM core
> PMUs. I'm always happy for as much testing as possible. The last code
> coverage number I have for Linux v6.17 is 38.6% of lines under
> tools/perf. Since then, I've added quite a bit of testing for commands
> like `perf top`. Perhaps we now cover over 50% of the lines of code.

Ok, incomplete tests are always better than no tests. I would add the test
although it looks not so pretty. :)

>
> Thanks,
> Ian
>
>>> Thanks,
>>> Ian
>>>
>>>>> Thanks,
>>>>> Ian
>>>>>
>>>>>> +}
>>>>>> +
>>>>>> test_ratio_to_prev() {
>>>>>> echo "ratio-to-prev test"
>>>>>> if ! perf record -o /dev/null -e "{instructions, cycles/period=100000,ratio-to-prev=0.5/}" \
>>>>>> @@ -457,6 +498,7 @@ test_leader_sampling
>>>>>> test_topdown_leader_sampling
>>>>>> test_precise_max
>>>>>> test_callgraph
>>>>>> +test_acr_sampling
>>>>>> test_ratio_to_prev
>>>>>>
>>>>>> # restore the default value
>>>>>>
>>>>>> base-commit: 4e03d6494f9504f8af46ba68a2a8b6877c196789
>>>>>> --
>>>>>> 2.34.1
>>>>>>