[PATCH v1 50/58] perf rwtop: Port rwtop to use python module

[Ian Rogers]

Port the legacy Perl script rwtop.pl to a python script using the perf
module in tools/perf/python.

The new script uses a class-based architecture and leverages the
perf.session API for event processing.

It periodically displays system-wide r/w call activity, broken down by
PID, refreshed every interval.

Complications:
- Implemented periodic display based on event timestamps
  (sample.sample_time) instead of relying on SIGALRM, making it robust
  for file-based processing.
- Used ANSI escape codes (\x1b[H\x1b[2J) to clear the terminal.
- Fixed unused imports and indentation issues identified by pylint.
- pylint warns about the module name not being snake_case, but it is
  kept for consistency with the original script name.

Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/python/rwtop.py | 179 +++++++++++++++++++++++++++++++++++++
 1 file changed, 179 insertions(+)
 create mode 100755 tools/perf/python/rwtop.py

diff --git a/tools/perf/python/rwtop.py b/tools/perf/python/rwtop.py
new file mode 100755
index 000000000000..e895b34b7114
--- /dev/null
+++ b/tools/perf/python/rwtop.py
@@ -0,0 +1,179 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-only
+"""Periodically displays system-wide r/w call activity, broken down by pid."""
+
+import argparse
+from collections import defaultdict
+import sys
+from typing import Optional, Dict, Any
+import perf
+
+class RwTop:
+    """Periodically displays system-wide r/w call activity."""
+    def __init__(self, interval: int = 3, nlines: int = 20) -> None:
+        self.interval_ns = interval * 1000000000
+        self.nlines = nlines
+        self.reads: Dict[int, Dict[str, Any]] = defaultdict(
+            lambda: {
+                "bytes_requested": 0,
+                "bytes_read": 0,
+                "total_reads": 0,
+                "comm": "",
+                "errors": defaultdict(int),
+            }
+        )
+        self.writes: Dict[int, Dict[str, Any]] = defaultdict(
+            lambda: {
+                "bytes_written": 0,
+                "total_writes": 0,
+                "comm": "",
+                "errors": defaultdict(int),
+            }
+        )
+        self.unhandled: Dict[str, int] = defaultdict(int)
+        self.session: Optional[perf.session] = None
+        self.last_print_time: int = 0
+
+    def process_event(self, sample: perf.sample_event) -> None:
+        """Process events."""
+        event_name = str(sample.evsel)
+        pid = sample.sample_pid
+        sample_time = sample.sample_time
+
+        if self.last_print_time == 0:
+            self.last_print_time = sample_time
+
+        # Check if interval has passed
+        if sample_time - self.last_print_time >= self.interval_ns:
+            self.print_totals()
+            self.last_print_time = sample_time
+
+        assert self.session is not None
+        try:
+            comm = self.session.process(pid).comm()
+        except Exception:  # pylint: disable=broad-except
+            comm = "unknown"
+
+        if "sys_enter_read" in event_name:
+            self._handle_sys_enter_read(sample, pid, comm)
+        elif "sys_exit_read" in event_name:
+            self._handle_sys_exit_read(sample, pid)
+        elif "sys_enter_write" in event_name:
+            self._handle_sys_enter_write(sample, pid, comm)
+        elif "sys_exit_write" in event_name:
+            self._handle_sys_exit_write(sample, pid)
+        else:
+            self.unhandled[event_name] += 1
+
+    def _handle_sys_enter_read(self, sample: perf.sample_event, pid: int, comm: str) -> None:
+        try:
+            count = sample.count
+            self.reads[pid]["bytes_requested"] += count
+            self.reads[pid]["total_reads"] += 1
+            self.reads[pid]["comm"] = comm
+        except AttributeError:
+            pass
+
+    def _handle_sys_exit_read(self, sample: perf.sample_event, pid: int) -> None:
+        try:
+            ret = sample.ret
+            if ret > 0:
+                self.reads[pid]["bytes_read"] += ret
+            else:
+                self.reads[pid]["errors"][ret] += 1
+        except AttributeError:
+            pass
+
+    def _handle_sys_enter_write(self, sample: perf.sample_event, pid: int, comm: str) -> None:
+        try:
+            count = sample.count
+            self.writes[pid]["bytes_written"] += count
+            self.writes[pid]["total_writes"] += 1
+            self.writes[pid]["comm"] = comm
+        except AttributeError:
+            pass
+
+    def _handle_sys_exit_write(self, sample: perf.sample_event, pid: int) -> None:
+        try:
+            ret = sample.ret
+            if ret <= 0:
+                self.writes[pid]["errors"][ret] += 1
+        except AttributeError:
+            pass
+
+    def print_totals(self) -> None:
+        """Print summary tables."""
+        # Clear terminal using ANSI escape codes
+        print("\x1b[H\x1b[2J", end="")
+
+        print("read counts by pid:\n")
+        print(
+            f"{'pid':>6s}  {'comm':<20s}  {'# reads':>10s}  "
+            f"{'bytes_req':>10s}  {'bytes_read':>10s}"
+        )
+        print(f"{'-'*6}  {'-'*20}  {'-'*10}  {'-'*10}  {'-'*10}")
+
+        count = 0
+        for pid, data in sorted(self.reads.items(),
+                                key=lambda kv: kv[1]["bytes_read"], reverse=True):
+            print(
+                f"{pid:6d}  {data['comm']:<20s}  {data['total_reads']:10d}  "
+                f"{data['bytes_requested']:10d}  {data['bytes_read']:10d}"
+            )
+            count += 1
+            if count >= self.nlines:
+                break
+
+        print("\nwrite counts by pid:\n")
+        print(f"{'pid':>6s}  {'comm':<20s}  {'# writes':>10s}  {'bytes_written':>13s}")
+        print(f"{'-'*6}  {'-'*20}  {'-'*10}  {'-'*13}")
+
+        count = 0
+        for pid, data in sorted(self.writes.items(),
+                                key=lambda kv: kv[1]["bytes_written"], reverse=True):
+            print(
+                f"{pid:6d}  {data['comm']:<20s}  "
+                f"{data['total_writes']:10d}  {data['bytes_written']:13d}"
+            )
+            count += 1
+            if count >= self.nlines:
+                break
+
+        # Reset counts
+        self.reads.clear()
+        self.writes.clear()
+
+    def run(self, input_file: str) -> None:
+        """Run the session."""
+        self.session = perf.session(perf.data(input_file), sample=self.process_event)
+        self.session.process_events()
+
+        # Print final totals if there are any left
+        if self.reads or self.writes:
+            self.print_totals()
+
+        if self.unhandled:
+            print("\nunhandled events:\n")
+            print(f"{'event':<40s}  {'count':>10s}")
+            print(f"{'-'*40}  {'-'*10}")
+            for event_name, count in self.unhandled.items():
+                print(f"{event_name:<40s}  {count:10d}")
+
+def main() -> None:
+    """Main function."""
+    parser = argparse.ArgumentParser(description="Trace r/w activity by PID")
+    parser.add_argument(
+        "interval", type=int, nargs="?", default=3, help="Refresh interval in seconds"
+    )
+    parser.add_argument("-i", "--input", default="perf.data", help="Input file")
+    args = parser.parse_args()
+
+    analyzer = RwTop(args.interval)
+    try:
+        analyzer.run(args.input)
+    except IOError as e:
+        print(e, file=sys.stderr)
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()
-- 
2.54.0.rc1.513.gad8abe7a5a-goog