#! /usr/bin/python3
#
# offcputime Summarize off-CPU time by stack trace
# For Linux, uses BCC, eBPF.
#
# USAGE: offcputime [-h] [-p PID | -t TID | -u | -k] [-U | -K] [-d] [-f] [-s]
# [--stack-storage-size STACK_STORAGE_SIZE]
# [-m MIN_BLOCK_TIME] [-M MAX_BLOCK_TIME] [--state STATE]
# [duration]
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 13-Jan-2016 Brendan Gregg Created this.
# 27-Mar-2023 Rocky Xing Added option to show symbol offsets.
# 04-Apr-2023 Rocky Xing Updated default stack storage size.
from __future__ import print_function
from bcc import BPF
from sys import stderr
import argparse
import errno
import signal
# arg validation
def positive_int(val):
try:
ival = int(val)
except ValueError:
raise argparse.ArgumentTypeError("must be an integer")
if ival < 0:
raise argparse.ArgumentTypeError("must be positive")
return ival
def positive_nonzero_int(val):
ival = positive_int(val)
if ival == 0:
raise argparse.ArgumentTypeError("must be nonzero")
return ival
def stack_id_err(stack_id):
# -EFAULT in get_stackid normally means the stack-trace is not available,
# Such as getting kernel stack trace in userspace code
return (stack_id < 0) and (stack_id != -errno.EFAULT)
# 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 -s 5 # 5 seconds, and show symbol offsets
./offcputime -m 1000 # trace only events that last more than 1000 usec
./offcputime -M 10000 # trace only events that last less than 10000 usec
./offcputime -p 185 # only trace threads for PID 185
./offcputime -t 188 # only trace thread 188
./offcputime -u # only trace user threads (no kernel)
./offcputime -k # only trace kernel threads (no user)
./offcputime -U # only show user space stacks (no kernel)
./offcputime -K # only show kernel space stacks (no user)
"""
parser = argparse.ArgumentParser(
description="Summarize off-CPU time by stack trace",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
thread_group = parser.add_mutually_exclusive_group()
# Note: this script provides --pid and --tid flags but their arguments are
# referred to internally using kernel nomenclature: TGID and PID.
thread_group.add_argument("-p", "--pid", metavar="PID", dest="tgid",
help="trace this PID only", type=positive_int)
thread_group.add_argument("-t", "--tid", metavar="TID", dest="pid",
help="trace this TID only", type=positive_int)
thread_group.add_argument("-u", "--user-threads-only", action="store_true",
help="user threads only (no kernel threads)")
thread_group.add_argument("-k", "--kernel-threads-only", action="store_true",
help="kernel threads only (no user threads)")
stack_group = parser.add_mutually_exclusive_group()
stack_group.add_argument("-U", "--user-stacks-only", action="store_true",
help="show stacks from user space only (no kernel space stacks)")
stack_group.add_argument("-K", "--kernel-stacks-only", action="store_true",
help="show stacks from kernel space only (no user space stacks)")
parser.add_argument("-d", "--delimited", action="store_true",
help="insert delimiter between kernel/user stacks")
parser.add_argument("-f", "--folded", action="store_true",
help="output folded format")
parser.add_argument("-s", "--offset", action="store_true",
help="show address offsets")
parser.add_argument("--stack-storage-size", default=16384,
type=positive_nonzero_int,
help="the number of unique stack traces that can be stored and "
"displayed (default 16384)")
parser.add_argument("duration", nargs="?", default=99999999,
type=positive_nonzero_int,
help="duration of trace, in seconds")
parser.add_argument("-m", "--min-block-time", default=1,
type=positive_nonzero_int,
help="the amount of time in microseconds over which we " +
"store traces (default 1)")
parser.add_argument("-M", "--max-block-time", default=(1 << 64) - 1,
type=positive_nonzero_int,
help="the amount of time in microseconds under which we " +
"store traces (default U64_MAX)")
parser.add_argument("--state", type=positive_int,
help="filter on this thread state bitmask (eg, 2 == TASK_UNINTERRUPTIBLE" +
") see include/linux/sched.h")
parser.add_argument("--ebpf", action="store_true",
help=argparse.SUPPRESS)
args = parser.parse_args()
folded = args.folded
duration = int(args.duration)
debug = 0
if args.folded and args.offset:
print("ERROR: can only use -f or -s. Exiting.")
exit()
# signal handler
def signal_ignore(signal, frame):
print()
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/sched.h>
#define MINBLOCK_US MINBLOCK_US_VALUEULL
#define MAXBLOCK_US MAXBLOCK_US_VALUEULL
struct key_t {
u32 pid;
u32 tgid;
int user_stack_id;
int kernel_stack_id;
char name[TASK_COMM_LEN];
};
BPF_HASH(counts, struct key_t);
BPF_HASH(start, u32);
BPF_STACK_TRACE(stack_traces, STACK_STORAGE_SIZE);
struct warn_event_t {
u32 pid;
u32 tgid;
u32 t_start;
u32 t_end;
};
BPF_PERF_OUTPUT(warn_events);
int oncpu(struct pt_regs *ctx, struct task_struct *prev) {
u32 pid = prev->pid;
u32 tgid = prev->tgid;
u64 ts, *tsp;
// record previous thread sleep time
if ((THREAD_FILTER) && (STATE_FILTER)) {
ts = bpf_ktime_get_ns();
start.update(&pid, &ts);
}
// get the current thread's start time
pid = bpf_get_current_pid_tgid();
tgid = bpf_get_current_pid_tgid() >> 32;
tsp = start.lookup(&pid);
if (tsp == 0) {
return 0; // missed start or filtered
}
// calculate current thread's delta time
u64 t_start = *tsp;
u64 t_end = bpf_ktime_get_ns();
start.delete(&pid);
if (t_start > t_end) {
struct warn_event_t event = {
.pid = pid,
.tgid = tgid,
.t_start = t_start,
.t_end = t_end,
};
warn_events.perf_submit(ctx, &event, sizeof(event));
return 0;
}
u64 delta = t_end - t_start;
delta = delta / 1000;
if ((delta < MINBLOCK_US) || (delta > MAXBLOCK_US)) {
return 0;
}
// create map key
struct key_t key = {};
key.pid = pid;
key.tgid = tgid;
key.user_stack_id = USER_STACK_GET;
key.kernel_stack_id = KERNEL_STACK_GET;
bpf_get_current_comm(&key.name, sizeof(key.name));
counts.increment(key, delta);
return 0;
}
"""
# set thread filter
thread_context = ""
if args.tgid is not None:
thread_context = "PID %d" % args.tgid
thread_filter = 'tgid == %d' % args.tgid
elif args.pid is not None:
thread_context = "TID %d" % args.pid
thread_filter = 'pid == %d' % args.pid
elif args.user_threads_only:
thread_context = "user threads"
thread_filter = '!(prev->flags & PF_KTHREAD)'
elif args.kernel_threads_only:
thread_context = "kernel threads"
thread_filter = 'prev->flags & PF_KTHREAD'
else:
thread_context = "all threads"
thread_filter = '1'
if args.state == 0:
state_filter = 'prev->STATE_FIELD == 0'
elif args.state:
# these states are sometimes bitmask checked
state_filter = 'prev->STATE_FIELD & %d' % args.state
else:
state_filter = '1'
bpf_text = bpf_text.replace('THREAD_FILTER', thread_filter)
bpf_text = bpf_text.replace('STATE_FILTER', state_filter)
if BPF.kernel_struct_has_field(b'task_struct', b'__state') == 1:
bpf_text = bpf_text.replace('STATE_FIELD', '__state')
else:
bpf_text = bpf_text.replace('STATE_FIELD', 'state')
# set stack storage size
bpf_text = bpf_text.replace('STACK_STORAGE_SIZE', str(args.stack_storage_size))
bpf_text = bpf_text.replace('MINBLOCK_US_VALUE', str(args.min_block_time))
bpf_text = bpf_text.replace('MAXBLOCK_US_VALUE', str(args.max_block_time))
# handle stack args
kernel_stack_get = "stack_traces.get_stackid(ctx, 0)"
user_stack_get = "stack_traces.get_stackid(ctx, BPF_F_USER_STACK)"
stack_context = ""
if args.user_stacks_only:
stack_context = "user"
kernel_stack_get = "-1"
elif args.kernel_stacks_only:
stack_context = "kernel"
user_stack_get = "-1"
else:
stack_context = "user + kernel"
bpf_text = bpf_text.replace('USER_STACK_GET', user_stack_get)
bpf_text = bpf_text.replace('KERNEL_STACK_GET', kernel_stack_get)
need_delimiter = args.delimited and not (args.kernel_stacks_only or
args.user_stacks_only)
# check for an edge case; the code below will handle this case correctly
# but ultimately nothing will be displayed
if args.kernel_threads_only and args.user_stacks_only:
print("ERROR: Displaying user stacks for kernel threads " +
"doesn't make sense.", file=stderr)
exit(2)
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
print("ERROR: Exiting")
exit(3)
# initialize BPF
b = BPF(text=bpf_text)
b.attach_kprobe(event_re=r'^finish_task_switch$|^finish_task_switch\.isra\.\d$',
fn_name="oncpu")
matched = b.num_open_kprobes()
if matched == 0:
print("error: 0 functions traced. Exiting.", file=stderr)
exit(4)
# header
if not folded:
print("Tracing off-CPU time (us) of %s by %s stack" %
(thread_context, stack_context), end="")
if duration < 99999999:
print(" for %d secs." % duration)
else:
print("... Hit Ctrl-C to end.")
def print_warn_event(cpu, data, size):
event = b["warn_events"].event(data)
# See https://github.com/iovisor/bcc/pull/3227 for those wondering how can this happen.
print("WARN: Skipped an event with negative duration: pid:%d, tgid:%d, off-cpu:%d, on-cpu:%d"
% (event.pid, event.tgid, event.t_start, event.t_end),
file=stderr)
b["warn_events"].open_perf_buffer(print_warn_event)
try:
duration_ms = duration * 1000
start_time_ms = int(BPF.monotonic_time() / 1000000)
while True:
elapsed_ms = int(BPF.monotonic_time() / 1000000) - start_time_ms
if elapsed_ms >= duration_ms:
break
b.perf_buffer_poll(timeout=duration_ms - elapsed_ms)
except KeyboardInterrupt:
# as cleanup can take many seconds, trap Ctrl-C:
signal.signal(signal.SIGINT, signal_ignore)
if not folded:
print()
show_offset = False
if args.offset:
show_offset = True
missing_stacks = 0
has_enomem = False
counts = b.get_table("counts")
stack_traces = b.get_table("stack_traces")
for k, v in sorted(counts.items(), key=lambda counts: counts[1].value):
# handle get_stackid errors
if not args.user_stacks_only and stack_id_err(k.kernel_stack_id):
missing_stacks += 1
has_enomem = has_enomem or k.kernel_stack_id == -errno.ENOMEM
if not args.kernel_stacks_only and stack_id_err(k.user_stack_id):
missing_stacks += 1
has_enomem = has_enomem or k.user_stack_id == -errno.ENOMEM
# user stacks will be symbolized by tgid, not pid, to avoid the overhead
# of one symbol resolver per thread
user_stack = [] if k.user_stack_id < 0 else \
stack_traces.walk(k.user_stack_id)
kernel_stack = [] if k.kernel_stack_id < 0 else \
stack_traces.walk(k.kernel_stack_id)
if folded:
# print folded stack output
user_stack = list(user_stack)
kernel_stack = list(kernel_stack)
line = [k.name.decode('utf-8', 'replace')]
# if we failed to get the stack is, such as due to no space (-ENOMEM) or
# hash collision (-EEXIST), we still print a placeholder for consistency
if not args.kernel_stacks_only:
if stack_id_err(k.user_stack_id):
line.append("[Missed User Stack]")
else:
line.extend([b.sym(addr, k.tgid).decode('utf-8', 'replace')
for addr in reversed(user_stack)])
if not args.user_stacks_only:
line.extend(["-"] if (need_delimiter and k.kernel_stack_id >= 0 and k.user_stack_id >= 0) else [])
if stack_id_err(k.kernel_stack_id):
line.append("[Missed Kernel Stack]")
else:
line.extend([b.ksym(addr).decode('utf-8', 'replace')
for addr in reversed(kernel_stack)])
print("%s %d" % (";".join(line), v.value))
else:
# print default multi-line stack output
if not args.user_stacks_only:
if stack_id_err(k.kernel_stack_id):
print(" [Missed Kernel Stack]")
else:
for addr in kernel_stack:
print(" %s" % b.ksym(addr, show_offset=show_offset).decode('utf-8', 'replace'))
if not args.kernel_stacks_only:
if need_delimiter and k.user_stack_id >= 0 and k.kernel_stack_id >= 0:
print(" --")
if stack_id_err(k.user_stack_id):
print(" [Missed User Stack]")
else:
for addr in user_stack:
print(" %s" % b.sym(addr, k.tgid, show_offset=show_offset).decode('utf-8', 'replace'))
print(" %-16s %s (%d)" % ("-", k.name.decode('utf-8', 'replace'), k.pid))
print(" %d\n" % v.value)
if missing_stacks > 0:
enomem_str = "" if not has_enomem else \
" Consider increasing --stack-storage-size."
print("WARNING: %d stack traces lost and could not be displayed.%s" %
(missing_stacks, enomem_str),
file=stderr)
Mini Shell