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285 lines
8.7 KiB
285 lines
8.7 KiB
#!/usr/bin/env python
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#
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# offwaketime Summarize blocked time by kernel off-CPU stack + waker stack
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# For Linux, uses BCC, eBPF.
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#
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# USAGE: offwaketime [-h] [-u] [-p PID] [-T] [duration]
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#
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# The current implementation uses an unrolled loop for x86_64, and was written
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# as a proof of concept. This implementation should be replaced in the future
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# with an appropriate bpf_ call, when available.
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#
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# The Off-CPU stack is currently limited to a stack trace depth of 20
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# (maxtdepth), and the waker stack limited to 10 (maxwdepth). This is also
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# limited to kernel stacks, and x86_64 only. Check for future versions, where
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# these limitations should be removed.
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#
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# Copyright 2016 Netflix, Inc.
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# Licensed under the Apache License, Version 2.0 (the "License")
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#
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# 20-Jan-2016 Brendan Gregg Created this.
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from __future__ import print_function
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from bcc import BPF
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from time import sleep
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import argparse
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import signal
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# arguments
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examples = """examples:
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./offwaketime # trace off-CPU + waker stack time until Ctrl-C
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./offwaketime 5 # trace for 5 seconds only
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./offwaketime -f 5 # 5 seconds, and output in folded format
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./offwaketime -u # don't include kernel threads (user only)
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./offwaketime -p 185 # trace fo PID 185 only
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"""
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parser = argparse.ArgumentParser(
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description="Summarize blocked time by kernel stack trace + waker stack",
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formatter_class=argparse.RawDescriptionHelpFormatter,
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epilog=examples)
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parser.add_argument("-u", "--useronly", action="store_true",
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help="user threads only (no kernel threads)")
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parser.add_argument("-p", "--pid",
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help="trace this PID only")
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parser.add_argument("-v", "--verbose", action="store_true",
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help="show raw addresses")
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parser.add_argument("-f", "--folded", action="store_true",
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help="output folded format")
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parser.add_argument("duration", nargs="?", default=99999999,
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help="duration of trace, in seconds")
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args = parser.parse_args()
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folded = args.folded
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duration = int(args.duration)
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debug = 0
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maxwdepth = 10 # and MAXWDEPTH
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maxtdepth = 20 # and MAXTDEPTH
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if args.pid and args.useronly:
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print("ERROR: use either -p or -u.")
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exit()
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# signal handler
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def signal_ignore(signal, frame):
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print()
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# define BPF program
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bpf_text = """
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#include <uapi/linux/ptrace.h>
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#include <linux/sched.h>
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#define MAXWDEPTH 10
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#define MAXTDEPTH 20
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#define MINBLOCK_US 1
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struct key_t {
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char waker[TASK_COMM_LEN];
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char target[TASK_COMM_LEN];
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u64 wret[MAXWDEPTH];
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u64 tret[MAXTDEPTH];
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};
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BPF_HASH(counts, struct key_t);
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BPF_HASH(start, u32);
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struct wokeby_t {
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char name[TASK_COMM_LEN];
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u64 ret[MAXWDEPTH];
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};
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BPF_HASH(wokeby, u32, struct wokeby_t);
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static u64 get_frame(u64 *bp) {
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if (*bp) {
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// The following stack walker is x86_64 specific
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u64 ret = 0;
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if (bpf_probe_read(&ret, sizeof(ret), (void *)(*bp+8)))
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return 0;
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if (bpf_probe_read(bp, sizeof(*bp), (void *)*bp))
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*bp = 0;
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if (ret < __START_KERNEL_map)
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return 0;
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return ret;
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}
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return 0;
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}
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int waker(struct pt_regs *ctx, struct task_struct *p) {
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u32 pid = p->pid;
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if (!(FILTER))
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return 0;
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u64 bp = 0;
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struct wokeby_t woke = {};
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int depth = 0;
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bpf_get_current_comm(&woke.name, sizeof(woke.name));
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bp = ctx->bp;
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// unrolled loop (MAXWDEPTH):
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
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woke.ret[depth] = get_frame(&bp);
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out:
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wokeby.update(&pid, &woke);
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return 0;
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}
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int oncpu(struct pt_regs *ctx, struct task_struct *p) {
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u32 pid = p->pid;
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u64 ts, *tsp;
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// record previous thread sleep time
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if (FILTER) {
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ts = bpf_ktime_get_ns();
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start.update(&pid, &ts);
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}
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// calculate current thread's delta time
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pid = bpf_get_current_pid_tgid();
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tsp = start.lookup(&pid);
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if (tsp == 0)
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return 0; // missed start or filtered
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u64 delta = bpf_ktime_get_ns() - *tsp;
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start.delete(&pid);
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delta = delta / 1000;
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if (delta < MINBLOCK_US)
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return 0;
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// create map key
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u64 zero = 0, *val, bp = 0;
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int depth = 0;
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struct key_t key = {};
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struct wokeby_t *woke;
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bpf_get_current_comm(&key.target, sizeof(key.target));
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bp = ctx->bp;
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// unrolled loop (MAXTDEPTH):
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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if (!(key.tret[depth++] = get_frame(&bp))) goto out;
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key.tret[depth] = get_frame(&bp);
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out:
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woke = wokeby.lookup(&pid);
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if (woke) {
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__builtin_memcpy(&key.wret, woke->ret, sizeof(key.wret));
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__builtin_memcpy(&key.waker, woke->name, TASK_COMM_LEN);
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wokeby.delete(&pid);
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}
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val = counts.lookup_or_init(&key, &zero);
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(*val) += delta;
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return 0;
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}
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"""
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if args.pid:
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filter = 'pid == %s' % args.pid
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elif args.useronly:
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filter = '!(p->flags & PF_KTHREAD)'
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else:
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filter = '1'
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bpf_text = bpf_text.replace('FILTER', filter)
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if debug:
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print(bpf_text)
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# initialize BPF
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b = BPF(text=bpf_text)
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b.attach_kprobe(event="finish_task_switch", fn_name="oncpu")
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b.attach_kprobe(event="try_to_wake_up", fn_name="waker")
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matched = b.num_open_kprobes()
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if matched == 0:
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print("0 functions traced. Exiting.")
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exit()
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# header
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if not folded:
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print("Tracing blocked time (us) by kernel off-CPU and waker stack",
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end="")
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if duration < 99999999:
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print(" for %d secs." % duration)
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else:
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print("... Hit Ctrl-C to end.")
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# output
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while (1):
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try:
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sleep(duration)
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except KeyboardInterrupt:
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# as cleanup can take many seconds, trap Ctrl-C:
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signal.signal(signal.SIGINT, signal_ignore)
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if not folded:
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print()
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counts = b.get_table("counts")
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for k, v in sorted(counts.items(), key=lambda counts: counts[1].value):
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if folded:
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# fold target stack
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line = k.target + ";"
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for i in reversed(range(0, maxtdepth)):
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if k.tret[i] == 0:
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continue
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line = line + b.ksym(k.tret[i])
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if i != 0:
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line = line + ";"
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# add delimiter
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line = line + ";-"
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# fold waker stack
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for i in range(0, maxwdepth):
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line = line + ";"
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if k.wret[i] == 0:
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break
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line = line + b.ksym(k.wret[i])
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if i != 0:
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line = line + ";" + k.waker
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# print as a line
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print("%s %d" % (line, v.value))
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else:
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# print wakeup name then stack in reverse order
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print(" %-16s %s" % ("waker:", k.waker))
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for i in reversed(range(0, maxwdepth)):
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if k.wret[i] == 0:
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continue
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print(" %-16x %s" % (k.wret[i],
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b.ksym(k.wret[i])))
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# print delimiter
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print(" %-16s %s" % ("-", "-"))
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# print default multi-line stack output
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for i in range(0, maxtdepth):
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if k.tret[i] == 0:
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break
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print(" %-16x %s" % (k.tret[i],
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b.ksym(k.tret[i])))
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print(" %-16s %s" % ("target:", k.target))
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print(" %d\n" % v.value)
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counts.clear()
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if not folded:
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print("Detaching...")
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exit()
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