Re: [PATCH 2/2] perf test: Add python JIT dump test

[Ian Rogers]

On Fri, Nov 14, 2025 at 1:29 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> Add a test case for the python interpreter like below so that we can
> make sure it won't break again.  To validate the effect of build-ID
> generation, it adds and removes the JIT'ed DSOs to/from the build-ID
> cache for the test.
>
>   $ perf test -vv jitdump
>    84: python profiling with jitdump:
>   --- start ---
>   test child forked, pid 214316
>   Run python with -Xperf_jit
>   [ perf record: Woken up 5 times to write data ]
>   [ perf record: Captured and wrote 1.180 MB /tmp/__perf_test.perf.data.XbqZNm (140 samples) ]
>   Generate JIT-ed DSOs using perf inject
>   Add JIT-ed DSOs to the build-ID cache
>   Check the symbol containing the script name
>   Found 108 matching lines
>   Remove JIT-ed DSOs from the build-ID cache
>   ---- end(0) ----
>    84: python profiling with jitdump                                   : Ok
>
> Cc: Pablo Galindo <pablogsal@xxxxxxxxx>
> Link: https://docs.python.org/3/howto/perf_profiling.html#how-to-work-without-frame-pointers
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
>  tools/perf/tests/shell/jitdump-python.sh | 41 ++++++++++++++++++++++++
>  tools/perf/tests/shell/jitdump-test.py   | 14 ++++++++
>  2 files changed, 55 insertions(+)
>  create mode 100755 tools/perf/tests/shell/jitdump-python.sh
>  create mode 100644 tools/perf/tests/shell/jitdump-test.py
>
> diff --git a/tools/perf/tests/shell/jitdump-python.sh b/tools/perf/tests/shell/jitdump-python.sh
> new file mode 100755
> index 0000000000000000..101c15e65da1a0c0
> --- /dev/null
> +++ b/tools/perf/tests/shell/jitdump-python.sh
> @@ -0,0 +1,41 @@
> +#!/bin/bash
> +# python profiling with jitdump
> +# SPDX-License-Identifier: GPL-2.0
> +
> +if ! command -v python > /dev/null; then
> +    echo "Skip: no python found"
> +    exit 2
> +fi

Can this just reuse the python set up logic in:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/shell/lib/setup_python.sh?h=perf-tools-next

> +
> +SHELLDIR=$(dirname $0)
> +PERF_DATA=$(mktemp /tmp/__perf_test.perf.data.XXXXXX)
> +
> +echo "Run python with -Xperf_jit"
> +perf record -k 1 -g --call-graph dwarf -o "${PERF_DATA}" -- python -Xperf_jit ${SHELLDIR}/jitdump-test.py

We can avoid an additional file by using the REPL, this is why the
java test is using jshell:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/shell/test_java_symbol.sh?h=perf-tools-next#n41

> +
> +_PID=$(perf report -i "${PERF_DATA}" -F pid -q -g none | cut -d: -f1 -s)
> +PID=$(echo -n $_PID)  # remove newlines
> +
> +echo "Generate JIT-ed DSOs using perf inject"
> +perf inject -i "${PERF_DATA}" -j -o "${PERF_DATA}.jit"

Thomas Richter did a workaround in the Java version to avoid debuginfod queries:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/tests/shell/test_java_symbol.sh?h=perf-tools-next#n59

> +
> +echo "Add JIT-ed DSOs to the build-ID cache"
> +for F in /tmp/jitted-${PID}-*.so; do
> +  perf buildid-cache -a "${F}"
> +done
> +
> +echo "Check the symbol containing the script name"
> +NUM=$(perf report -i "${PERF_DATA}.jit" -s sym | grep -c jitdump-test.py)
> +
> +echo "Found ${NUM} matching lines"
> +
> +echo "Remove JIT-ed DSOs from the build-ID cache"
> +for F in /tmp/jitted-${PID}-*.so; do
> +  perf buildid-cache -r "${F}"
> +done
> +
> +rm -f ${PERF_DATA} ${PERF_DATA}.jit /tmp/jit-${PID}.dump /tmp/jitted-${PID}-*.so

It'd be nice to have this in a function that also gets run if there is
a trap. It looks like the Java test is missing a call to cleanup_files
on the success path.

Thanks,
Ian

> +
> +if [ "${NUM}" -eq 0 ]; then
> +    exit 1
> +fi
> diff --git a/tools/perf/tests/shell/jitdump-test.py b/tools/perf/tests/shell/jitdump-test.py
> new file mode 100644
> index 0000000000000000..b427363ae4956db6
> --- /dev/null
> +++ b/tools/perf/tests/shell/jitdump-test.py
> @@ -0,0 +1,14 @@
> +def foo(n):
> +    result = 0
> +    for _ in range(n):
> +        result += 1
> +    return result
> +
> +def bar(n):
> +    foo(n)
> +
> +def baz(n):
> +    bar(n)
> +
> +if __name__ == "__main__":
> +    baz(1000000)
> --
> 2.52.0.rc1.455.g30608eb744-goog
>