1 files changed, 72 insertions, 0 deletions
diff --git a/research/experiments/022-tpcc-grouped/owner-samples.py b/research/experiments/022-tpcc-grouped/owner-samples.py
new file mode 100644
index 0000000..5415cf6
--- /dev/null
+++ b/research/experiments/022-tpcc-grouped/owner-samples.py
@@ -0,0 +1,72 @@
+#!/usr/bin/env python3
+"""Where pure-serve's owner thread is: its stack sampled with gdb (a poor man's profiler; perf is not on this Pi).
+
+    owner-samples.py SAMPLES OUT.txt
+
+Waits for a pure-serve with a pure-owner thread, then attaches gdb SAMPLES
+times, a little apart, and keeps the owner's stack each time. Prints how
+many samples had each serve.c phase on the stack, and the innermost frames.
+"""
+import collections
+import re
+import subprocess
+import sys
+import time
+from pathlib import Path
+
+samples, out = int(sys.argv[1]), Path(sys.argv[2])
+
+
+def owner():
+    for proc in Path('/proc').iterdir():
+        if not proc.name.isdigit():
+            continue
+        try:
+            if (proc / 'comm').read_text().strip() != 'pure-serve':
+                continue
+            for task in (proc / 'task').iterdir():
+                if (task / 'comm').read_text().strip() == 'pure-owner':
+                    return int(proc.name), int(task.name)
+        except OSError:
+            continue
+    return None
+
+
+found = None
+while not found:
+    found = owner()
+    time.sleep(0.2)
+pid, tid = found
+time.sleep(10)  # past loading, into the run
+stacks = []
+for _ in range(samples):
+    text = subprocess.run(['gdb', '-batch', '-nx', '-p', str(pid), '-ex', 'set pagination off',
+                           '-ex', 'thread apply all bt 40'], capture_output=True, text=True).stdout
+    # The owner's section: from its "Thread ... (LWP tid)" header to the next thread's.
+    match = re.search(rf'Thread [^\n]*\(LWP {tid}\)[^\n]*\n(.*?)(?=\nThread |\Z)', text, re.S)
+    if match:
+        frames = re.findall(r'^#\d+\s+(?:0x[0-9a-f]+ in )?(\S+)', match.group(1), re.M)
+        stacks.append(frames)
+    time.sleep(0.3)
+out.write_text('\n'.join(' < '.join(s) for s in stacks) + '\n')
+phases = collections.Counter()
+inner = collections.Counter()
+for frames in stacks:
+    names = set(frames)
+    phase = ('waiting' if names & {'pthread_cond_wait', 'pthread_cond_timedwait', '__futex_abstimed_wait_common'}
+             and not names & {'execute'} else
+             'publish' if 'publish' in names else
+             'checkpoint_round' if 'checkpoint_round' in names else
+             'feed_outlets' if 'feed_outlets' in names else
+             'save' if 'save_burst' in names else
+             'hand_back' if 'hand_back' in names else
+             'apply' if 'apply_effect' in names else
+             'other')
+    phases[phase] += 1
+    inner[frames[0] if frames else '?'] += 1
+print(f'{len(stacks)} samples of the owner (pid {pid}, thread {tid})')
+for phase, n in phases.most_common():
+    print(f'  {phase:<18} {n:>4}  {n / max(len(stacks), 1):.0%}')
+print('innermost frames:')
+for name, n in inner.most_common(15):
+    print(f'  {name:<40} {n:>4}')