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Copy pathrunqlat.py
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executable file
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#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# runqlat Run queue (scheduler) latency as a histogram.
# For Linux, uses BCC, eBPF.
#
# USAGE: runqlat [-h] [-T] [-m] [-P] [-L] [-p PID] [interval] [count]
#
# This measures the time a task spends waiting on a run queue for a turn
# on-CPU, and shows this time as a histogram. This time should be small, but a
# task may need to wait its turn due to CPU load.
#
# This measures two types of run queue latency:
# 1. The time from a task being enqueued on a run queue to its context switch
# and execution. This traces enqueue_task_*() -> finish_task_switch(),
# and instruments the run queue latency after a voluntary context switch.
# 2. The time from when a task was involuntary context switched and still
# in the runnable state, to when it next executed. This is instrumented
# from finish_task_switch() alone.
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 07-Feb-2016 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
from time import sleep, strftime
import argparse
# arguments
examples = """examples:
./runqlat # summarize run queue latency as a histogram
./runqlat 1 10 # print 1 second summaries, 10 times
./runqlat -mT 1 # 1s summaries, milliseconds, and timestamps
./runqlat -P # show each PID separately
./runqlat -p 185 # trace PID 185 only
"""
parser = argparse.ArgumentParser(
description="Summarize run queue (scheduler) latency as a histogram",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-T", "--timestamp", action="store_true",
help="include timestamp on output")
parser.add_argument("-m", "--milliseconds", action="store_true",
help="millisecond histogram")
parser.add_argument("-P", "--pids", action="store_true",
help="print a histogram per process ID")
# PID options are --pid and --pids, so namespaces should be --pidns (not done
# yet) and --pidnss:
parser.add_argument("--pidnss", action="store_true",
help="print a histogram per PID namespace")
parser.add_argument("-L", "--tids", action="store_true",
help="print a histogram per thread ID")
parser.add_argument("-p", "--pid",
help="trace this PID only")
parser.add_argument("interval", nargs="?", default=99999999,
help="output interval, in seconds")
parser.add_argument("count", nargs="?", default=99999999,
help="number of outputs")
args = parser.parse_args()
countdown = int(args.count)
debug = 0
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/sched.h>
#include <linux/nsproxy.h>
#include <linux/pid_namespace.h>
typedef struct pid_key {
u64 id; // work around
u64 slot;
} pid_key_t;
typedef struct pidns_key {
u64 id; // work around
u64 slot;
} pidns_key_t;
BPF_HASH(start, u32);
STORAGE
struct rq;
// record enqueue timestamp
int trace_enqueue(struct pt_regs *ctx, struct rq *rq, struct task_struct *p,
int flags)
{
u32 tgid = p->tgid;
u32 pid = p->pid;
if (FILTER)
return 0;
u64 ts = bpf_ktime_get_ns();
start.update(&pid, &ts);
return 0;
}
// calculate latency
int trace_run(struct pt_regs *ctx, struct task_struct *prev)
{
u32 pid, tgid;
// ivcsw: treat like an enqueue event and store timestamp
if (prev->state == TASK_RUNNING) {
tgid = prev->tgid;
pid = prev->pid;
if (!(FILTER)) {
u64 ts = bpf_ktime_get_ns();
start.update(&pid, &ts);
}
}
tgid = bpf_get_current_pid_tgid() >> 32;
pid = bpf_get_current_pid_tgid();
if (FILTER)
return 0;
u64 *tsp, delta;
// fetch timestamp and calculate delta
tsp = start.lookup(&pid);
if (tsp == 0) {
return 0; // missed enqueue
}
delta = bpf_ktime_get_ns() - *tsp;
FACTOR
// store as histogram
STORE
start.delete(&pid);
return 0;
}
"""
# code substitutions
if args.pid:
# pid from userspace point of view is thread group from kernel pov
bpf_text = bpf_text.replace('FILTER', 'tgid != %s' % args.pid)
else:
bpf_text = bpf_text.replace('FILTER', '0')
if args.milliseconds:
bpf_text = bpf_text.replace('FACTOR', 'delta /= 1000000;')
label = "msecs"
else:
bpf_text = bpf_text.replace('FACTOR', 'delta /= 1000;')
label = "usecs"
if args.pids or args.tids:
section = "pid"
pid = "tgid"
if args.tids:
pid = "pid"
section = "tid"
bpf_text = bpf_text.replace('STORAGE',
'BPF_HISTOGRAM(dist, pid_key_t);')
bpf_text = bpf_text.replace('STORE',
'pid_key_t key = {.id = ' + pid + ', .slot = bpf_log2l(delta)}; ' +
'dist.increment(key);')
elif args.pidnss:
section = "pidns"
bpf_text = bpf_text.replace('STORAGE',
'BPF_HISTOGRAM(dist, pidns_key_t);')
bpf_text = bpf_text.replace('STORE', 'pidns_key_t key = ' +
'{.id = prev->nsproxy->pid_ns_for_children->ns.inum, ' +
'.slot = bpf_log2l(delta)}; dist.increment(key);')
else:
section = ""
bpf_text = bpf_text.replace('STORAGE', 'BPF_HISTOGRAM(dist);')
bpf_text = bpf_text.replace('STORE',
'dist.increment(bpf_log2l(delta));')
if debug:
print(bpf_text)
# load BPF program
b = BPF(text=bpf_text)
b.attach_kprobe(event_re="enqueue_task_*", fn_name="trace_enqueue")
b.attach_kprobe(event="finish_task_switch", fn_name="trace_run")
print("Tracing run queue latency... Hit Ctrl-C to end.")
# output
exiting = 0 if args.interval else 1
dist = b.get_table("dist")
while (1):
try:
sleep(int(args.interval))
except KeyboardInterrupt:
exiting = 1
print()
if args.timestamp:
print("%-8s\n" % strftime("%H:%M:%S"), end="")
dist.print_log2_hist(label, section, section_print_fn=int)
dist.clear()
countdown -= 1
if exiting or countdown == 0:
exit()