linux-kernel - Re: [PATCH v5 10/10] perf probe: Support SDT markers having reference counter (semaphore)

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Message-Id: <20180702145727.GC65296@linux.vnet.ibm.com>
Date:   Mon, 2 Jul 2018 07:57:27 -0700
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     oleg@...hat.com, rostedt@...dmis.org, mhiramat@...nel.org,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org, corbet@....net,
        linux-doc@...r.kernel.org, ananth@...ux.vnet.ibm.com,
        alexis.berlemont@...il.com, naveen.n.rao@...ux.vnet.ibm.com,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
        linux@...linux.org.uk, ralf@...ux-mips.org, paul.burton@...s.com
Subject: Re: [PATCH v5 10/10] perf probe: Support SDT markers having
 reference counter (semaphore)

* Ravi Bangoria <ravi.bangoria@...ux.ibm.com> [2018-06-28 10:52:09]:

> With this, perf buildid-cache will save SDT markers with reference
> counter in probe cache. Perf probe will be able to probe markers
> having reference counter. Ex,
> 
>   # readelf -n /tmp/tick | grep -A1 loop2
>     Name: loop2
>     ... Semaphore: 0x0000000010020036
> 
>   # ./perf buildid-cache --add /tmp/tick

Would this perf buildid-cache work if the executable is stripped of
symbols?

>   # ./perf probe sdt_tick:loop2
>   # ./perf stat -e sdt_tick:loop2 /tmp/tick
>     hi: 0
>     hi: 1
>     hi: 2
>     ^C
>      Performance counter stats for '/tmp/tick':
>                  3      sdt_tick:loop2
>        2.561851452 seconds time elapsed

Also can we document how to use SDT markers with perf under perf-probe
or perf-build-cache?