linux-kernel - Re: [PATCH 2/8] perf metrics: fix parse errors in cascade lake metrics

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Date:   Wed, 22 Apr 2020 08:34:02 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Haiyan Song <haiyanx.song@...el.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        John Garry <john.garry@...wei.com>,
        Leo Yan <leo.yan@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 2/8] perf metrics: fix parse errors in cascade lake metrics

On Wed, Apr 22, 2020 at 7:38 AM Andi Kleen <ak@...ux.intel.com> wrote:
>
> On Wed, Apr 22, 2020 at 12:48:03AM -0700, Ian Rogers wrote:
> > Remove over escaping with \\.
> > Remove extraneous if 1 if 0 == 1 else 0 else 0.
>
> So where do these parse errors happen exactly? Some earlier
> patches introduced them as regressions?

I'll work to track down a Fixes tag. I can repro the Skylakex errors
without the test in this series, by doing:

$ perf stat -M DRAM_Read_Latency sleep 1
Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument)
for event (cha/event=0x36\,uma
sk=0x21/).
/bin/dmesg | grep -i perf may provide additional information.

This was just the escaping issue. I'm less clear on the other cascade
lake issue, and it is a bit more work for me to test on cascade lake.
What is "if 1 if 0 == 1 else 0 else 0" trying to do? Perhaps hunting
for the Fixes will let me know, but it looks like a copy-paste error.

> The original metrics worked without parse errors as far as I know.

The skylake issue above repros on 5.2.17 and so it seems like it is
broken for a while. The test in this series will prevent this in the
future, but without this patch that test fails.

> If it fixes something earlier it would need Fixes: tags.

Working on it. Thanks for the input!

Ian

> -Andi