linux-kernel - Re: [PATCH][Ping] perf test: Test 17 fails with make LIBPFM4=1 on s390 z/VM

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Date:   Thu, 20 May 2021 08:21:12 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Thomas Richter <tmricht@...ux.ibm.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        sumanth Korikkar <sumanthk@...ux.ibm.com>,
        Stephane Eranian <eranian@...gle.com>, svens@...ux.ibm.com,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>
Subject: Re: [PATCH][Ping] perf test: Test 17 fails with make LIBPFM4=1 on
 s390 z/VM

On Thu, May 20, 2021 at 6:52 AM Thomas Richter <tmricht@...ux.ibm.com> wrote:
>
> This test case fails on s390 virtual machine z/VM which has no PMU support
> when the perf tool is built with LIBPFM4=1.
>
> Using make LIBPFM4=1 builds the perf tool with support for libpfm
> event notation. The command line flag --pfm-events is valid:
>  # ./perf record --pfm-events cycles -- true
>  [ perf record: Woken up 1 times to write data ]
>  [ perf record: Captured and wrote 0.001 MB perf.data (2 samples) ]
>  #
>
> However the command 'perf test -Fv 17' fails on s390 z/VM virtual machine
> with LIBPFM4=1:
>   # perf test -Fv 17
>   17: Setup struct perf_event_attr                                    :
>   --- start ---
>   .....
>   running './tests/attr/test-record-group2'
>   unsupp  './tests/attr/test-record-group2'
>   running './tests/attr/test-record-pfm-period'
>   expected exclude_hv=0, got 1
>  FAILED './tests/attr/test-record-pfm-period' - match failure
>  ---- end ----
>  Setup struct perf_event_attr: FAILED!
>
> When --pfm-event system is not supported, the test returns unsupported
> and continues. Here is an example using a virtual machine on x86 and
> Fedora 34:
>  [root@f33 perf]# perf test -Fv 17
>  17: Setup struct perf_event_attr                                    :
>  --- start ---
>  .....
>  running './tests/attr/test-record-group2'
>  unsupp  './tests/attr/test-record-group2'
>  running './tests/attr/test-record-pfm-period'
>  unsupp  './tests/attr/test-record-pfm-period'
>  ....
>
> The issue is file ./tests/attr/test-record-pfm-period
> which requires perf event attribute member exclude_hv to be zero.
> This is not the case on s390 where the value of exclude_hv is one when
> executing on a z/VM virtual machine without PMU hardware support.
>
> Fix this by allowing value exlucde_hv to be zero or one.
>
> Output before:
>  # /usr/bin/python ./tests/attr.py -d ./tests/attr/ -t \
>         test-record-pfm-period -p ./perf  -vvv 2>&1| fgrep match
>     matching [event:base-record]
>     match: [event:base-record] matches []
>  FAILED './tests/attr//test-record-pfm-period' - match failure
>  #
>
> Output after:
>  # /usr/bin/python ./tests/attr.py -d ./tests/attr/ -t \
>         test-record-pfm-period -p ./perf  -vvv 2>&1| fgrep match
>     matching [event:base-record]
>     match: [event:base-record] matches ['event-1-0-6', 'event-1-0-5']
>   matched
>     matching [event-1-0-6]
>     match: [event-1-0-6] matches ['event:base-record']
>     matching [event-1-0-5]
>     match: [event-1-0-5] matches ['event:base-record']
>   matched
>  #
>
> Background:
> Using libpfm library ends up in this function call sequence
>
> pfm_get_perf_event_encoding()
> +-- pfm_get_os_event_encoding()
>     +-- pfmlib_perf_event_encode()
>
> is called when no hardware specific PMU unit can be detected
> as in the s390 z/VM virtual machine case. This uses the
> "perf_events generic PMU" data structure which sets exclude_hv per default.
> Using this PMU that test case always fails.
>
> That is the reason why exclude_hv attribute setting varies.
>
> Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
> Cc: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/tests/attr/test-record-pfm-period | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/tools/perf/tests/attr/test-record-pfm-period b/tools/perf/tests/attr/test-record-pfm-period
> index 368f5b814094..b962d6d11ee2 100644
> --- a/tools/perf/tests/attr/test-record-pfm-period
> +++ b/tools/perf/tests/attr/test-record-pfm-period
> @@ -7,3 +7,4 @@ ret     = 1
>  sample_period=77777
>  sample_type=7
>  freq=0
> +exclude_hv=0|1

Presumably you see the same failure for other attribute checks, such
as test-record-period? Would it make more sense to change base-record
so that exclude_hv=0|1 ?

Thanks,
Ian

> --
> 2.30.2
>