linux-kernel - Re: [PATCH 08/14] perf test: Add memcpy thread test shell script

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Message-ID: <13803152-48c9-4db0-7ff8-2f34dde53cbc@arm.com>
Date:   Tue, 5 Jul 2022 15:28:00 +0100
From:   James Clark <james.clark@....com>
To:     carsten.haitzler@...s.arm.com, linux-kernel@...r.kernel.org
Cc:     coresight@...ts.linaro.org, mathieu.poirier@...aro.org,
        mike.leach@...aro.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org, Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH 08/14] perf test: Add memcpy thread test shell script



On 05/07/2022 15:25, James Clark wrote:
> 
> 
> On 01/07/2022 13:07, carsten.haitzler@...s.arm.com wrote:
>> From: "Carsten Haitzler (Rasterman)" <raster@...terman.com>
>>
>> Add a script to drive the threaded memcpy test that gathers data so
>> it passes a minimum bar for amount and quality of content that we
>> extract from the kernel's perf support.
>>
> 
> On this one I get a failure about 1/50 times on N1SDP (I ran it about 150
> times and saw 3 failures so it's quite consistent). Usually it records
> about a 1.4MB file with one aux record. But when it fails the file is
> only 20K and has one small aux record:
> 
>    0 0 0x1a10 [0x30]: PERF_RECORD_AUXTRACE size: 0x1820  offset: 0  ref: 0x1c23126d7ff3d2ab  idx: 3  tid: 682799  cpu: 3
> 
> Nothing was dropped, and the load on the system wasn't any different
> to when it passes. So I'm not sure if this is a real coresight bug
> or that the test is flaky. There was a bug in SPE before where
> threads weren't followed after forking, but only very rarely. It feels
> a bit like that.
> 
> It could also be some contention issue because 10 threads are launched
> but the machine only has 4 cores.
> 
> The failure message from the test looks like this:
> 
>    77: CoreSight / Memcpy 16k 10 Threads                               :
>    --- start ---
>    Couldn't synthesize bpf events.
>    [ perf record: Woken up 1 times to write data ]
>    [ perf record: Captured and wrote 0.012 MB ./perf-memcpy_thread-16k_10.data ]
>    Sanity check number of ASYNC is too low (3 < 10)
>     ---- end ----
>    CoreSight / Memcpy 16k 10 Threads: FAILED!
> 
> I didn't see this issue on any of the other tests. Sometimes very small
> files were made if I loaded the system, but the tests still passed.

Spoke too soon, same thing on another test with an unloaded system. It's
just a bit more rare:

  80: CoreSight / Unroll Loop Thread 10                               :
  --- start ---
  Couldn't synthesize bpf events.
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.041 MB ./perf-unroll_loop_thread-10.data ]
  Sanity check number of ASYNC is too low (6 < 10)
  ---- end ----
  CoreSight / Unroll Loop Thread 10: FAILED!

> 
> Thanks
> James
> 
>> Signed-off-by: Carsten Haitzler <carsten.haitzler@....com>
>> ---
>>  .../shell/coresight/memcpy_thread_16k_10.sh    | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>  create mode 100755 tools/perf/tests/shell/coresight/memcpy_thread_16k_10.sh
>>
>> diff --git a/tools/perf/tests/shell/coresight/memcpy_thread_16k_10.sh b/tools/perf/tests/shell/coresight/memcpy_thread_16k_10.sh
>> new file mode 100755
>> index 000000000000..d21ba8545938
>> --- /dev/null
>> +++ b/tools/perf/tests/shell/coresight/memcpy_thread_16k_10.sh
>> @@ -0,0 +1,18 @@
>> +#!/bin/sh -e
>> +# CoreSight / Memcpy 16k 10 Threads
>> +
>> +# SPDX-License-Identifier: GPL-2.0
>> +# Carsten Haitzler <carsten.haitzler@....com>, 2021
>> +
>> +TEST="memcpy_thread"
>> +. $(dirname $0)/../lib/coresight.sh
>> +ARGS="16 10 1"
>> +DATV="16k_10"
>> +DATA="$DATD/perf-$TEST-$DATV.data"
>> +
>> +perf record $PERFRECOPT -o "$DATA" "$BIN" $ARGS
>> +
>> +perf_dump_aux_verify "$DATA" 10 10 10
>> +
>> +err=$?
>> +exit $err
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