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

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Date:   Sat, 9 Dec 2017 01:12:06 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Paul Clarke <pc@...ibm.com>
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 Fri, 8 Dec 2017 08:49:46 -0600
Paul Clarke <pc@...ibm.com> wrote:

> 
> 
> 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)

Yes, this style, since the symbols are recorded with version suffixes.

Thank you,

> 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
> 
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-- 
Masami Hiramatsu <mhiramat@...nel.org>