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

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Date:   Thu, 23 Apr 2020 12:10:30 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Jin, Yao" <yao.jin@...ux.intel.com>
Cc:     Ian Rogers <irogers@...gle.com>, Andi Kleen <ak@...ux.intel.com>,
        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>,
        Namhyung Kim <namhyung@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Haiyan Song <haiyanx.song@...el.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 Thu, Apr 23, 2020 at 03:51:18PM +0800, Jin, Yao wrote:
> Hi Ian,
> 
> On 4/23/2020 2:09 PM, Ian Rogers wrote:
> > On Wed, Apr 22, 2020 at 10:54 PM Jin, Yao <yao.jin@...ux.intel.com> wrote:
> > > 
> > > Hi Jiri,
> > > 
> > > Bisected to this commit which introduced the regression.
> > > 
> > > 26226a97724d ("perf expr: Move expr lexer to flex")
> > > 
> > > Would you like to look at that?
> > 
> > Hi Jin,
> > 
> > that commit breaks parsing of things like ','. See fixes in this patch
> > set such as:
> > https://lore.kernel.org/lkml/20200422220430.254014-5-irogers@google.com/
> > Fixing the lex issues then exposes other bugs that need to be
> > corrected in the json. I've added Fixes to the commit message of:
> > https://lore.kernel.org/lkml/20200422220430.254014-3-irogers@google.com/
> > https://lore.kernel.org/lkml/20200422220430.254014-4-irogers@google.com/
> > and would be glad of a review. If we can land:
> > https://lore.kernel.org/lkml/20200422220430.254014-12-irogers@google.com/
> > then expr as the source of parse errors can go away :-) The next
> > problem is the parse events code, but some of that logic is dependent
> > on the machine it is running on. It'd be good to add a test that
> > parsed events code can handle the events in metrics too, filtering out
> > things like duration_time that are special to metrics.
> > 
> > Thanks,
> > Ian
> > 
> 
> Only with the fix
> "https://lore.kernel.org/lkml/20200422220430.254014-5-irogers@google.com/"
> (without other json modifications), the issue was still there.
> 
> localhost:~ # perf stat -M DRAM_Read_Latency
> event syntax error:
> '../event=0x36,,umask=0x21/,cha/event=0x35,cha_0/event=0x0/}:W,duration_time'
>                                   \___ parser error
> 
>  Usage: perf stat [<options>] [<command>]
> 
>     -M, --metrics <metric/metric group list>
>                           monitor specified metrics or metric groups
> (separated by ,)

hum, I don't have that metric, is there another example of broken metric?

[jolsa@...va perf]$ sudo ./perf stat -M DRAM_Read_Latency
Cannot find metric or group `DRAM_Read_Latency'

> 
> So you added other commits which changed the json to let the parse work. But
> I don't know if we have to do with this way because it should be a
> regression issue.
> 
> In my opinion, we'd better fix the issue in 26226a97724d ("perf expr: Move
> expr lexer to flex") and try not to change the json if possible.

yea, that change definitely had a potential of breaking things ;-)
but it should be easy to fix them

I'll go through the v3 of the patchset

thanks,
jirka