linux-kernel - Re: [PATCH v2 2/5] perf-probe: Cut off the version suffix from event name

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Date:   Fri, 8 Dec 2017 08:49:46 -0600
From:   Paul Clarke <pc@...ibm.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        bhargavb <bhargavaramudu@...il.com>,
        linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>,
        linux-rt-users@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 2/5] perf-probe: Cut off the version suffix from event
 name



On 12/07/2017 09:01 PM, Masami Hiramatsu wrote:
> On Thu, 7 Dec 2017 10:34:51 -0600
> Paul Clarke <pc@...ibm.com> wrote:
>> On 12/07/2017 01:20 AM, Masami Hiramatsu wrote:
>>> Cut off the version suffix (e.g. @GLIBC_2.2.5 etc.) from
>>> automatic generated event name. This fixes wildcard event
>>> adding like below case;
>>>
>>>   =====
>>>   # perf probe -x /lib64/libc-2.25.so malloc*
>>>   Internal error: "malloc_get_state@...BC_2" is wrong event name.
>>>     Error: Failed to add events.
>>>   =====
>>>
>>> This failure was caused by a versioned suffix symbol.
>>> With this fix, perf probe automatically cuts the
>>> suffix after @ as below.
>>>
>>>   =====
>>>   # ./perf probe -x /lib64/libc-2.25.so malloc*
>>>   Added new events:
>>>     probe_libc:malloc_printerr (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_consolidate (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_check (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_hook_ini (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc    (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_trim (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_usable_size (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_stats (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_info (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:mallochook (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_get_state (on malloc* in /usr/lib64/libc-2.25.so)
>>>     probe_libc:malloc_set_state (on malloc* in /usr/lib64/libc-2.25.so)
>>>
>>>   You can now use it in all perf tools, such as:
>>>
>>> 	  perf record -e probe_libc:malloc_set_state -aR sleep 1
>>>
>>>   =====
>>
>> I think this will still fall over for a case where there are multiple versions of the same base symbol, like:
>>
>> $ nm /lib64/libc.so.6 | egrep ' sched_getaffinity'
>> 0000000000134430 T sched_getaffinity@...BC_2.3.3
>> 00000000000dcf00 T sched_getaffinity@@GLIBC_2.3.4
> 
> No, in that case perf probe adds number suffix (_1, _2...) for new events :)
> 
> This feature (number suffix) is anyway required for the case that inlined
> function is spreaded in multiple places. I think this is natural for perf probe.

I can live with that.

Is the versioning tag retained for display with "perf probe -l" display, so the probe points can be distinguished?

In other words, will one see:
# perf probe -l
  probe_libc:sched_getaffinity (on sched_getaffinity@...BC_2.3.3 in /usr/lib64/libc-2.17.so)
  probe_libc:sched_getaffinity_1 (on sched_getaffinity@@GLIBC_2.3.4 in /usr/lib64/libc-2.17.so)
or
# perf probe -l
  probe_libc:sched_getaffinity (on sched_getaffinity in /usr/lib64/libc-2.17.so)
  probe_libc:sched_getaffinity_1 (on sched_getaffinity in /usr/lib64/libc-2.17.so)

PC