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

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Date:   Wed, 13 Dec 2017 00:02:55 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Paul Clarke <pc@...ibm.com>,
        Masami Hiramatsu <mhiramat@...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 Mon, 11 Dec 2017 15:25:47 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Em Fri, Dec 08, 2017 at 08:49:46AM -0600, Paul Clarke escreveu:
> > 
> > 
> > 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)
> 
> [root@...et ~]# 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
> 
> [root@...et ~]# perf probe -l
>   probe_libc:malloc    (on 0xd22a6973 in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_check (on 0x25db6f5a in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_consolidate (on 0x88f7c44a in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_get_state (on 0xdd38eca7 in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_hook_ini (on 0x8de2b533 in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_info (on 0x8b327bde in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_printerr (on 0x8fff087c in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_set_state (on 0x861940e6 in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_stats (on 0x51fa3cdc in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_trim (on 0xa9fa4e43 in /usr/lib64/libc-2.25.so)
>   probe_libc:malloc_usable_size (on 0xceb5e090 in /usr/lib64/libc-2.25.so)
>   probe_libc:mallochook (on 0x6ebc00f5 in /usr/lib64/libc-2.25.so)

This looks something wrong. perf-probe should try to get symbol
at least. What happened on that ? Could you run perf probe -l with -vv ?

On my Fedora26, 

$ sudo ./perf probe -l
  probe_libc:malloc    (on __malloc in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_check (on malloc_check in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_consolidate (on malloc_consolidate.part.1 in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_get_state (on malloc_get_state@...BC_2.2.5 in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_hook_ini (on malloc_hook_ini in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_info (on __malloc_info in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_printerr (on malloc_printerr in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_set_state (on malloc_set_state@...BC_2.2.5 in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_stats (on __malloc_stats in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_trim (on __malloc_trim in /usr/lib64/libc-2.25.so)
  probe_libc:malloc_usable_size (on __malloc_usable_size in /usr/lib64/libc-2.25.so)
  probe_libc:mallochook (on mallochook in /usr/lib64/libc-2.25.so)

I can see the symbols with version suffixes.


> [root@...et ~]#
> 
> [acme@...et perf]$ nm /lib64/libc-2.25.so | grep malloc_get_state
> 0000000000151ba0 T malloc_get_state@...BC_2.2.5
> [acme@...et perf]$
> 
> For your example it finds two symbols, adds two but I couldn't find a
> simple way of mapping one to the other, would be nice if 'perf probe -l'
> showed them like 'nm' does.
> 
> [root@...et ~]# nm /lib64/libc-2.25.so | grep ' sched_getaffinity'
> 0000000000151cd0 T sched_getaffinity@...BC_2.3.3
> 00000000000f3c10 T sched_getaffinity@@GLIBC_2.3.4
> [root@...et ~]#
> 
> [root@...et ~]# perf probe -x /lib64/libc-2.25.so sched_getaffinity*
> Added new events:
>   probe_libc:sched_getaffinity (on sched_getaffinity* in /usr/lib64/libc-2.25.so)
>   probe_libc:sched_getaffinity_1 (on sched_getaffinity* in /usr/lib64/libc-2.25.so)
> 
> You can now use it in all perf tools, such as:
> 
> 	perf record -e probe_libc:sched_getaffinity_1 -aR sleep 1
> 
> [root@...et ~]# perf probe -l
>   probe_libc:sched_getaffinity (on 0x5fd95e7c in /usr/lib64/libc-2.25.so)
>   probe_libc:sched_getaffinity_1 (on 0xd8d51601 in /usr/lib64/libc-2.25.so)
> [root@...et ~]#

This case also shows

$ sudo ./perf probe -l
  probe_libc:sched_getaffinity (on __sched_getaffinity_new in /usr/lib64/libc-2.25.so)
  probe_libc:sched_getaffinity_1 (on sched_getaffinity@...BC_2.3.3 in /usr/lib64/libc-2.25.so)

(but the first one seems a bit different, maybe it is an alias of sched_getaffinity@<some new version>.)

Thank you,

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