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sync_count.py
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sync_count.py
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#!/usr/bin/python
#
# sync_timing.py Trace time between syncs.
# For Linux, uses BCC, eBPF. Embedded C.
#
# Written as a basic example of tracing time between events.
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
from __future__ import print_function
from bcc import BPF
from bcc.utils import printb
# load BPF program
b = BPF(text="""
#include <uapi/linux/ptrace.h>
BPF_HASH(last);
struct trace_result_t {
u64 ts;
u64 delta;
u64 count;
};
BPF_PERF_OUTPUT(result);
int do_trace(struct pt_regs *ctx) {
u64 ts, *tsp, delta, key = 0, index=1, count = 0;
struct trace_result_t data;
// attempt to read stored timestamp
tsp = last.lookup(&key);
if (tsp != 0) {
delta = bpf_ktime_get_ns() - *tsp;
if (delta < 1000000000) {
tsp = last.lookup(&index);
if (tsp != NULL) {
count = *tsp;
count++;
}
data.ts = bpf_ktime_get_ns();
data.delta = delta / 1000000;
data.count = count;
result.perf_submit(ctx, &data, sizeof(data));
}
last.delete(&key);
last.delete(&index);
}
// update stored timestamp
ts = bpf_ktime_get_ns();
last.update(&key, &ts);
last.update(&index, &count);
return 0;
}
""")
b.attach_kprobe(event=b.get_syscall_fnname("sync"), fn_name="do_trace")
print("Tracing for quick sync's... Ctrl-C to end")
start = 0
def print_data(cpu, data, size):
global start
event = b["result"].event(data)
if start == 0:
start = event.ts
ts = event.ts - start
printb(b"At time %.2f s: multiple syncs detected, last %s ms ago, count %d" % (ts, event.delta, event.count))
b["result"].open_perf_buffer(print_data)
while True:
try:
b.perf_buffer_poll()
except KeyboardInterrupt:
exit()