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

[Ian Rogers]

On Wed, Aug 3, 2022 at 8:25 AM Leo Yan <leo.yan@xxxxxxxxxx> wrote:
>
> Hi Arnaldo, Ian,
>
> On Mon, Aug 01, 2022 at 09:38:23AM -0300, Arnaldo Carvalho de Melo wrote:
>
> [...]
>
> > I also think we could have something like a 'perf test' mode where, when
> > asked to, it would enable tests that involve downloading such files to
> > perform tests, such as this dacapo benchmark, and then would test if the
> > output matches expectations.
>
> I am working on testing script for java symbols, one of the steps shared by
> Ian is:
>
>   # /tmp/perf/perf record -k 1 java -agentpath:/tmp/perf/libperf-jvmti.so \
>     -jar dacapo-9.12-MR1-bach.jar -n 10 fop
>
> 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.

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.

Thanks,
Ian

> Thanks,
> Leo