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#!/usr/bin/python3
#
# trace-cmd record -e hrtimer_start -e hrtimer_cancel -e hrtimer_expire_entry -- $cmd
#
from tracecmd import *
def load_kallsyms(file_path='/proc/kallsyms'):
"""
Parses /proc/kallsyms into a dictionary.
Returns: { address_int: symbol_name }
"""
kallsyms_map = {}
try:
with open(file_path, 'r') as f:
for line in f:
# The format is: [address] [type] [name] [module]
parts = line.split()
if len(parts) < 3:
continue
addr = int(parts[0], 16)
name = parts[2]
kallsyms_map[addr] = name
except PermissionError:
print(f"Error: Permission denied reading {file_path}. Try running with sudo.")
except FileNotFoundError:
print(f"Error: {file_path} not found.")
return kallsyms_map
ksyms = load_kallsyms()
# pending[timer_ptr] = {'ts': timestamp, 'comm': comm}
pending = {}
# histograms[comm][bucket] = count
histograms = {}
class OnlineHarmonicMean:
def __init__(self):
self.n = 0 # Count of elements
self.S = 0.0 # Cumulative sum of reciprocals
def update(self, x):
if x == 0:
raise ValueError("Harmonic mean is undefined for zero.")
self.n += 1
self.S += 1.0 / x
return self.n / self.S
@property
def mean(self):
return self.n / self.S if self.n > 0 else 0
ohms = {}
def handle_start(record):
func_name = ksyms[record.num_field("function")]
if "rseq_slice_expired" in func_name:
timer_ptr = record.num_field("hrtimer")
pending[timer_ptr] = {
'ts': record.ts,
'comm': record.comm
}
return None
def handle_cancel(record):
timer_ptr = record.num_field("hrtimer")
if timer_ptr in pending:
start_data = pending.pop(timer_ptr)
duration_ns = record.ts - start_data['ts']
duration_us = duration_ns // 1000
comm = start_data['comm']
if comm not in ohms:
ohms[comm] = OnlineHarmonicMean()
ohms[comm].update(duration_ns)
if comm not in histograms:
histograms[comm] = {}
histograms[comm][duration_us] = histograms[comm].get(duration_us, 0) + 1
return None
def handle_expire(record):
timer_ptr = record.num_field("hrtimer")
if timer_ptr in pending:
start_data = pending.pop(timer_ptr)
comm = start_data['comm']
if comm not in histograms:
histograms[comm] = {}
# Record -1 bucket for expired (failed to cancel)
histograms[comm][-1] = histograms[comm].get(-1, 0) + 1
return None
if __name__ == "__main__":
t = Trace("trace.dat")
for cpu in range(0, t.cpus):
ev = t.read_event(cpu)
while ev:
if "hrtimer_start" in ev.name:
handle_start(ev)
if "hrtimer_cancel" in ev.name:
handle_cancel(ev)
if "hrtimer_expire_entry" in ev.name:
handle_expire(ev)
ev = t.read_event(cpu)
print("\n" + "="*40)
print("RSEQ SLICE HISTOGRAM (us)")
print("="*40)
for comm, buckets in histograms.items():
print(f"\nTask: {comm} Mean: {ohms[comm].mean:.3f} ns")
print(f" {'Latency (us)':<15} | {'Count'}")
print(f" {'-'*30}")
# Sort buckets numerically, putting -1 at the top
for bucket in sorted(buckets.keys()):
label = "EXPIRED" if bucket == -1 else f"{bucket} us"
print(f" {label:<15} | {buckets[bucket]}")
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