offwaketime.py for older kernels (#977)

tools/old/offwaketime.py

+#!/usr/bin/python
+#
+# offwaketime   Summarize blocked time by kernel off-CPU stack + waker stack
+#               For Linux, uses BCC, eBPF.
+#
+# USAGE: offwaketime [-h] [-u] [-p PID] [-T] [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.
+#
+# The Off-CPU stack is currently limited to a stack trace depth of 20
+# (maxtdepth), and the waker stack limited to 10 (maxwdepth). This is also
+# limited to kernel stacks, and x86_64 only. Check for future versions, where
+# these limitations should be removed.
+#
+# Copyright 2016 Netflix, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License")
+#
+# 20-Jan-2016   Brendan Gregg   Created this.
+
+from __future__ import print_function
+from bcc import BPF
+from time import sleep
+import argparse
+import signal
+
+# arguments
+examples = """examples:
+    ./offwaketime             # trace off-CPU + waker stack time until Ctrl-C
+    ./offwaketime 5           # trace for 5 seconds only
+    ./offwaketime -f 5        # 5 seconds, and output in folded format
+    ./offwaketime -u          # don't include kernel threads (user only)
+    ./offwaketime -p 185      # trace fo PID 185 only
+"""
+parser = argparse.ArgumentParser(
+    description="Summarize blocked time by kernel stack trace + waker stack",
+    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
+maxwdepth = 10    # and MAXWDEPTH
+maxtdepth = 20    # and MAXTDEPTH
+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 <uapi/linux/ptrace.h>
+#include <linux/sched.h>
+
+#define MAXWDEPTH	10
+#define MAXTDEPTH	20
+#define MINBLOCK_US	1
+
+struct key_t {
+    char waker[TASK_COMM_LEN];
+    char target[TASK_COMM_LEN];
+    u64 wret[MAXWDEPTH];
+    u64 tret[MAXTDEPTH];
+};
+BPF_HASH(counts, struct key_t);
+BPF_HASH(start, u32);
+struct wokeby_t {
+    char name[TASK_COMM_LEN];
+    u64 ret[MAXWDEPTH];
+};
+BPF_HASH(wokeby, u32, struct wokeby_t);
+
+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 waker(struct pt_regs *ctx, struct task_struct *p) {
+    u32 pid = p->pid;
+
+    if (!(FILTER))
+        return 0;
+
+    u64 bp = 0;
+    struct wokeby_t woke = {};
+    int depth = 0;
+    bpf_get_current_comm(&woke.name, sizeof(woke.name));
+    bp = ctx->bp;
+
+    // unrolled loop (MAXWDEPTH):
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    if (!(woke.ret[depth++] = get_frame(&bp))) goto out;
+    woke.ret[depth] = get_frame(&bp);
+
+out:
+    wokeby.update(&pid, &woke);
+    return 0;
+}
+
+int oncpu(struct pt_regs *ctx, struct task_struct *p) {
+    u32 pid = p->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 = {};
+    struct wokeby_t *woke;
+    bpf_get_current_comm(&key.target, sizeof(key.target));
+    bp = ctx->bp;
+
+    // unrolled loop (MAXTDEPTH):
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    if (!(key.tret[depth++] = get_frame(&bp))) goto out;
+    key.tret[depth] = get_frame(&bp);
+
+out:
+    woke = wokeby.lookup(&pid);
+    if (woke) {
+        __builtin_memcpy(&key.wret, woke->ret, sizeof(key.wret));
+        __builtin_memcpy(&key.waker, woke->name, TASK_COMM_LEN);
+        wokeby.delete(&pid);
+    }
+
+    val = counts.lookup_or_init(&key, &zero);
+    (*val) += delta;
+    return 0;
+}
+"""
+if args.pid:
+    filter = 'pid == %s' % args.pid
+elif args.useronly:
+    filter = '!(p->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")
+b.attach_kprobe(event="try_to_wake_up", fn_name="waker")
+matched = b.num_open_kprobes()
+if matched == 0:
+    print("0 functions traced. Exiting.")
+    exit()
+
+# header
+if not folded:
+    print("Tracing blocked time (us) by kernel off-CPU and waker 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:
+            # fold target stack
+            line = k.target + ";"
+            for i in reversed(range(0, maxtdepth)):
+                if k.tret[i] == 0:
+                    continue
+                line = line + b.ksym(k.tret[i])
+                if i != 0:
+                    line = line + ";"
+
+            # add delimiter
+            line = line + ";-"
+
+            # fold waker stack
+            for i in range(0, maxwdepth):
+                line = line + ";"
+                if k.wret[i] == 0:
+                    break
+                line = line + b.ksym(k.wret[i])
+            if i != 0:
+                line = line + ";" + k.waker
+
+            # print as a line
+            print("%s %d" % (line, v.value))
+        else:
+            # print wakeup name then stack in reverse order
+            print("    %-16s %s" % ("waker:", k.waker))
+            for i in reversed(range(0, maxwdepth)):
+                if k.wret[i] == 0:
+                    continue
+                print("    %-16x %s" % (k.wret[i],
+                    b.ksym(k.wret[i])))
+
+            # print delimiter
+            print("    %-16s %s" % ("-", "-"))
+
+            # print default multi-line stack output
+            for i in range(0, maxtdepth):
+                if k.tret[i] == 0:
+                    break
+                print("    %-16x %s" % (k.tret[i],
+                    b.ksym(k.tret[i])))
+            print("    %-16s %s" % ("target:", k.target))
+            print("        %d\n" % v.value)
+    counts.clear()
+
+    if not folded:
+        print("Detaching...")
+    exit()