linux-kernel - Re: [PATCH] perf symbol: Fail to read phdr workaround

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Date:   Thu, 4 Aug 2022 09:21:58 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf symbol: Fail to read phdr workaround

On Wed, Aug 03, 2022 at 05:26:39PM -0700, Ian Rogers wrote:

[...]

> > The question is how we can specify the path for the lib
> > libperf-jvmti.so in the testing script?
> >
> > If we can run the test case from the root folder of Linux kernel
> > source code, the lib libperf-jvmti.so can be found in the folder
> > $linux/tools/perf, but for the integration testing the lib should be
> > placed in an installed folder.  Any suggestion if we have exited
> > way to specify the path for libperf-jvmti.so, or need to introduce a
> > new shell envorinment variable for the lib path?
> 
> There is a hack in 'perf test' where we assume a few paths to tests:
> https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/tests/builtin-test.c?h=perf/core#n308
> so in this case we could look in the same directory. There is also a
> #define for PERF_EXEC_PATH.

Thanks for the info.  I will try to search paths like the buildin-test.c
file, and the lib libperf-jvmti.so is installed in the folder
"$HOME/lib64/", I will check if can reuse PERF_EXEC_PATH for this
case.

> I'd prefer it if the test could be self contained for example:
> 
> echo "int fib(int x) { return x > 1 ? fib(x - 2) + fib(x - 1) : 1; }
> int q = 0; for(int i=0; i < 10; i++) q += fib(i);
> System.out.println(q);" | /tmp/perf/perf record -k 1 jshell
> -J-agentpath:/tmp/perf/libperf-jvmti.so
> 
> where jshell runs on the JVM and so we should get some jitted execution time.

Will do.  Appreciate for sharing this!

Leo