linux-kernel - Re: [PATCH 1/3] perf, tools: Handle events including .c and .o

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Message-ID: <57F86FE0.5010105@huawei.com>
Date:   Sat, 8 Oct 2016 12:02:40 +0800
From:   "Wangnan (F)" <wangnan0@...wei.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Andi Kleen <andi@...stfloor.org>
CC:     <sukadev@...ux.vnet.ibm.com>, <jolsa@...hat.com>,
        <linux-kernel@...r.kernel.org>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/3] perf, tools: Handle events including .c and .o



On 2016/10/7 4:18, Arnaldo Carvalho de Melo wrote:
> Em Wed, Oct 05, 2016 at 12:47:10PM -0700, Andi Kleen escreveu:
>> From: Andi Kleen <ak@...ux.intel.com>
>>
>> This is a generic bug fix, but it helps with Sukadev's JSON event tree
>> where such events can happen.
>>
>> Any event inclduing a .c/.o/.bpf currently triggers BPF compilation or loading
>> and then an error.  This can happen for some Intel JSON events, which cannot
>> be used.
>>
>> Fix the scanner to only match for .o or .c or .bpf at the end.
>> This will prevent loading multiple BPF scripts separated with comma,
>> but I assume this is acceptable.
> So, I tried it with the example provided in the thread for a previous
> version of this patch (IIRC) and it still fails:
>
>
> [acme@...et linux]$ perf stat -e '{unc_p_clockticks,unc_p_power_state_occupancy.cores_c0}' -a -I 1000
> ERROR: problems with path {unc_p_clockticks,unc_p_power_state_occupancy.c: No such file or directory
> event syntax error: '{unc_p_clockticks,unc_p_power_state_occupancy.cores_c0}'
>                       \___ Failed to load {unc_p_clockticks,unc_p_power_state_occupancy.c from source: Error when compiling BPF scriptlet
>
> (add -v to see detail)
> Run 'perf list' for a list of valid events
>
>   Usage: perf stat [<options>] [<command>]
>
>      -e, --event <event>   event selector. use 'perf list' to list available events
> [acme@...et linux]$
>
> And with another event that for sure is available on this machine:
>
>
>
> [acme@...et linux]$ perf stat -e '{uops_executed.core_cycles_ge_2}' -I 1000 usleep 10
> ERROR: problems with path {uops_executed.c: No such file or directory
> event syntax error: '{uops_executed.core_cycles_ge_2}'
>                       \___ Failed to load {uops_executed.c from source: Error when compiling BPF scriptlet
>
> (add -v to see detail)
> Run 'perf list' for a list of valid events
>
>   Usage: perf stat [<options>] [<command>]
>
>      -e, --event <event>   event selector. use 'perf list' to list available events
> [acme@...et linux]$
>
>
> I thought this was due to the Makefile not noticing the change in the .l files, but I made
> sure I deleted the build dir and rebuilt from scratch, same problem.
>
> - Arnaldo
>   

Tested again, and thank you for giving us another chance for fixing this :)

The key problem here is not the ending '$' but the leading '{'. Flex's
greedy maching policy makes this problem.

According to the design of parse-events.l, when it see something like
'...{...}...', it first matches a 'group' in '<event>' scope, then rewind
to INITIAL scope to match events in the group. In INITIAL scope, when
it see a '{', flex consume this char and goes back to '<event>' scope
to match next event. It works well before match BPF file path using
unlimited '.*\.c' because '.*' will match the leading '{' in INITIAL
scope without consuming it.

The simplest method for this problem is fixing the '.*' part: like
what we define for 'event', don't match ',', '{' and '}'. Doesn't
like 'event', '/' is required because this is a path.

Will post a patch for it. Please test it again.

Thank you.