[PATCH 1/2] Read perf data file header from the file user specified with -i option for perf script flamegraph

[PATCH 1/2] Read perf data file header from the file user specified with -i option for perf script flamegraph

[Tianyou Li]

If specify the perf data file with -i option, the script will try to read the header information
regardless of the file name specified, instead it will try to access the perf.data. This simple
patch use the file name from -i option for command perf report --header-only to read the header.

Signed-off-by: Tianyou Li <tianyou.li@intel.com>
Reviewed-by: Pan Deng <pan.deng@intel.com>
Reviewed-by: Zhiguo Zhou <zhiguo.zhou@intel.com>
Reviewed-by: Wangyang Guo <wangyang.guo@intel.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
---
 tools/perf/scripts/python/flamegraph.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/scripts/python/flamegraph.py b/tools/perf/scripts/python/flamegraph.py
index cf7ce8229a6c..4f82dfea0a70 100755
--- a/tools/perf/scripts/python/flamegraph.py
+++ b/tools/perf/scripts/python/flamegraph.py
@@ -123,7 +123,13 @@ class FlameGraphCLI:
             return ""
 
         try:
-            output = subprocess.check_output(["perf", "report", "--header-only"])
+            # if the file name other than perf.data is given,
+            # we read the header of that file
+            if self.args.input:
+                output = subprocess.check_output(["perf", "report", "--header-only", "-i", self.args.input])
+            else:
+                output = subprocess.check_output(["perf", "report", "--header-only"])
+
             return output.decode("utf-8")
         except Exception as err:  # pylint: disable=broad-except
             print("Error reading report header: {}".format(err), file=sys.stderr)
-- 
2.47.1

[PATCH 2/2] Add -e option to focus on the specific event for generating the flamegraph

[Tianyou Li]

When processing the perf data file generated with multiple events,
the flamegraph script will count all the events regardless of
different event names.

This patch tries to add a -e option to specify the event name that
the flamegraph will be generated accordingly. If the -e option omitted,
the behavior remains unchanged.

Signed-off-by: Tianyou Li <tianyou.li@intel.com>
Reviewed-by: Pan Deng <pan.deng@intel.com>
Reviewed-by: Zhiguo Zhou <zhiguo.zhou@intel.com>
Reviewed-by: Wangyang Guo <wangyang.guo@intel.com>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
---
 tools/perf/scripts/python/flamegraph.py | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/perf/scripts/python/flamegraph.py b/tools/perf/scripts/python/flamegraph.py
index 4f82dfea0a70..e49ff242b779 100755
--- a/tools/perf/scripts/python/flamegraph.py
+++ b/tools/perf/scripts/python/flamegraph.py
@@ -94,6 +94,11 @@ class FlameGraphCLI:
         return child
 
     def process_event(self, event):
+        # ignore events where the event name does not match
+        # the one specified by the user
+        if self.args.event_name and event.get("ev_name") != self.args.event_name:
+            return
+
         pid = event.get("sample", {}).get("pid", 0)
         # event["dso"] sometimes contains /usr/lib/debug/lib/modules/*/vmlinux
         # for user-space processes; let's use pid for kernel or user-space distinction
@@ -130,7 +135,10 @@ class FlameGraphCLI:
             else:
                 output = subprocess.check_output(["perf", "report", "--header-only"])
 
-            return output.decode("utf-8")
+            result = output.decode("utf-8")
+            if self.args.event_name:
+                result += "\nFocused event: " + self.args.event_name
+            return result
         except Exception as err:  # pylint: disable=broad-except
             print("Error reading report header: {}".format(err), file=sys.stderr)
             return ""
@@ -241,6 +249,11 @@ if __name__ == "__main__":
                         default=False,
                         action="store_true",
                         help="allow unprompted downloading of HTML template")
+    parser.add_argument("-e", "--event",
+                        default="",
+                        dest="event_name",
+                        type=str,
+                        help="specify the event to generate flamegraph for")
 
     cli_args = parser.parse_args()
     cli = FlameGraphCLI(cli_args)
-- 
2.47.1

Re: [PATCH 1/2] Read perf data file header from the file user specified with -i option for perf script flamegraph

[Namhyung Kim]

On Tue, 10 Jun 2025 12:04:22 +0800, Tianyou Li wrote:
> If specify the perf data file with -i option, the script will try to read the header information
> regardless of the file name specified, instead it will try to access the perf.data. This simple
> patch use the file name from -i option for command perf report --header-only to read the header.
> 
> 
Applied to perf-tools-next, thanks!

Best regards,
Namhyung

RE: [PATCH 1/2] Read perf data file header from the file user specified with -i option for perf script flamegraph

[Li, Tianyou]

Appreciated for your kindly review. Thanks.

-----Original Message-----
From: Namhyung Kim <namhyung@kernel.org> 
Sent: Wednesday, June 25, 2025 1:53 AM
To: Peter Zijlstra <peterz@infradead.org>; Ingo Molnar <mingo@redhat.com>; Arnaldo Carvalho de Melo <acme@kernel.org>; Li, Tianyou <tianyou.li@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>; Alexander Shishkin <alexander.shishkin@linux.intel.com>; Jiri Olsa <jolsa@kernel.org>; Ian Rogers <irogers@google.com>; Hunter, Adrian <adrian.hunter@intel.com>; Kan Liang <kan.liang@linux.intel.com>; Guo, Wangyang <wangyang.guo@intel.com>; linux-perf-users@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] Read perf data file header from the file user specified with -i option for perf script flamegraph

On Tue, 10 Jun 2025 12:04:22 +0800, Tianyou Li wrote:
> If specify the perf data file with -i option, the script will try to 
> read the header information regardless of the file name specified, 
> instead it will try to access the perf.data. This simple patch use the file name from -i option for command perf report --header-only to read the header.
> 
> 
Applied to perf-tools-next, thanks!

Best regards,
Namhyung