#!/usr/bin/python # # offcputime Summarize off-CPU time by kernel stack trace # For Linux, uses BCC, eBPF. # # USAGE: offcputime [-h] [-u] [-p PID] [-v] [-f] [duration] # # The current implementation uses an unrolled loop for x86_64, and was written # as a proof of concept. This implementation should be replaced in the future # with an appropriate bpf_ call, when available. # # Currently limited to a stack trace depth of 21 (maxdepth + 1). # # Copyright 2016 Netflix, Inc. # Licensed under the Apache License, Version 2.0 (the "License") # # 13-Jan-2016 Brendan Gregg Created this. from __future__ import print_function from bcc import BPF from time import sleep, strftime import argparse import signal # arguments examples = """examples: ./offcputime # trace off-CPU stack time until Ctrl-C ./offcputime 5 # trace for 5 seconds only ./offcputime -f 5 # 5 seconds, and output in folded format ./offcputime -u # don't include kernel threads (user only) ./offcputime -p 185 # trace fo PID 185 only """ parser = argparse.ArgumentParser( description="Summarize off-CPU time by kernel stack trace", formatter_class=argparse.RawDescriptionHelpFormatter, epilog=examples) parser.add_argument("-u", "--useronly", action="store_true", help="user threads only (no kernel threads)") parser.add_argument("-p", "--pid", help="trace this PID only") parser.add_argument("-v", "--verbose", action="store_true", help="show raw addresses") parser.add_argument("-f", "--folded", action="store_true", help="output folded format") parser.add_argument("duration", nargs="?", default=99999999, help="duration of trace, in seconds") args = parser.parse_args() folded = args.folded duration = int(args.duration) debug = 0 maxdepth = 20 # and MAXDEPTH if args.pid and args.useronly: print("ERROR: use either -p or -u.") exit() # signal handler def signal_ignore(signal, frame): print() # define BPF program bpf_text = """ #include #include #define MAXDEPTH 20 #define MINBLOCK_US 1 struct key_t { char name[TASK_COMM_LEN]; // Skip saving the ip u64 ret[MAXDEPTH]; }; BPF_HASH(counts, struct key_t); BPF_HASH(start, u32); static u64 get_frame(u64 *bp) { if (*bp) { // The following stack walker is x86_64 specific u64 ret = 0; if (bpf_probe_read(&ret, sizeof(ret), (void *)(*bp+8))) return 0; if (bpf_probe_read(bp, sizeof(*bp), (void *)*bp)) *bp = 0; if (ret < __START_KERNEL_map) return 0; return ret; } return 0; } int oncpu(struct pt_regs *ctx, struct task_struct *prev) { u32 pid = prev->pid; u64 ts, *tsp; // record previous thread sleep time if (FILTER) { ts = bpf_ktime_get_ns(); start.update(&pid, &ts); } // calculate current thread's delta time pid = bpf_get_current_pid_tgid(); tsp = start.lookup(&pid); if (tsp == 0) return 0; // missed start or filtered u64 delta = bpf_ktime_get_ns() - *tsp; start.delete(&pid); delta = delta / 1000; if (delta < MINBLOCK_US) return 0; // create map key u64 zero = 0, *val, bp = 0; int depth = 0; struct key_t key = {}; bpf_get_current_comm(&key.name, sizeof(key.name)); bp = ctx->bp; // unrolled loop (MAXDEPTH): if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; if (!(key.ret[depth++] = get_frame(&bp))) goto out; out: val = counts.lookup_or_init(&key, &zero); (*val) += delta; return 0; } """ if args.pid: filter = 'pid == %s' % args.pid elif args.useronly: filter = '!(prev->flags & PF_KTHREAD)' else: filter = '1' bpf_text = bpf_text.replace('FILTER', filter) if debug: print(bpf_text) # initialize BPF b = BPF(text=bpf_text) b.attach_kprobe(event="finish_task_switch", fn_name="oncpu") matched = b.num_open_kprobes() if matched == 0: print("0 functions traced. Exiting.") exit() # header if not folded: print("Tracing off-CPU time (us) by kernel stack", end="") if duration < 99999999: print(" for %d secs." % duration) else: print("... Hit Ctrl-C to end.") # output while (1): try: sleep(duration) except KeyboardInterrupt: # as cleanup can take many seconds, trap Ctrl-C: signal.signal(signal.SIGINT, signal_ignore) if not folded: print() counts = b.get_table("counts") for k, v in sorted(counts.items(), key=lambda counts: counts[1].value): if folded: # print folded stack output line = k.name.decode('utf-8', 'replace') + ";" for i in reversed(range(0, maxdepth)): if k.ret[i] == 0: continue line = line + b.ksym(k.ret[i]) if i != 0: line = line + ";" print("%s %d" % (line, v.value)) else: # print default multi-line stack output for i in range(0, maxdepth): if k.ret[i] == 0: break print(" %-16x %s" % (k.ret[i], b.ksym(k.ret[i]))) print(" %-16s %s" % ("-", k.name)) print(" %d\n" % v.value) counts.clear() if not folded: print("Detaching...") exit()