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

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Message-ID: <f6b21fa9-7e0b-cb0d-d708-cfd7f3f53087@arm.com>
Date:   Tue, 5 Jul 2022 15:25:05 +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 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.

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