hardirqs.py

#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# hardirqs  Summarize hard IRQ (interrupt) event time.
#           For Linux, uses BCC, eBPF.
#
# USAGE: hardirqs [-h] [-T] [-Q] [-m] [-D] [interval] [count]
#
# Thanks Amer Ather for help understanding irq behavior.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 19-Oct-2015   Brendan Gregg   Created this.

from __future__ import print_function
from bcc import BPF
from time import sleep, strftime
import argparse

# arguments
examples = """examples:
    ./hardirqs            # sum hard irq event time
    ./hardirqs -d         # show hard irq event time as histograms
    ./hardirqs 1 10       # print 1 second summaries, 10 times
    ./hardirqs -NT 1      # 1s summaries, nanoseconds, and timestamps
"""
parser = argparse.ArgumentParser(
    description="Summarize hard irq event time as histograms",
    formatter_class=argparse.RawDescriptionHelpFormatter,
    epilog=examples)
parser.add_argument("-T", "--timestamp", action="store_true",
    help="include timestamp on output")
parser.add_argument("-N", "--nanoseconds", action="store_true",
    help="output in nanoseconds")
parser.add_argument("-d", "--dist", action="store_true",
    help="show distributions as histograms")
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)
if args.nanoseconds:
    factor = 1
    label = "nsecs"
else:
    factor = 1000
    label = "usecs"
debug = 0

# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/irq.h>
#include <linux/irqdesc.h>
#include <linux/interrupt.h>

typedef struct irq_key {
    char name[32];
    u64 slot;
} irq_key_t;
BPF_HASH(start, u32);
BPF_HASH(irqdesc, u32, struct irq_desc *);
BPF_HISTOGRAM(dist, irq_key_t);

// time IRQ
int trace_start(struct pt_regs *ctx, struct irq_desc *desc)
{
    u32 pid = bpf_get_current_pid_tgid();
    u64 ts = bpf_ktime_get_ns();
    start.update(&pid, &ts);
    irqdesc.update(&pid, &desc);
    return 0;
}

int trace_completion(struct pt_regs *ctx)
{
    u64 *tsp, delta;
    struct irq_desc **descp;
    u32 pid = bpf_get_current_pid_tgid();

    // fetch timestamp and calculate delta
    tsp = start.lookup(&pid);
    descp = irqdesc.lookup(&pid);
    if (tsp == 0 || descp == 0) {
        return 0;   // missed start
    }
    // Note: descp is a value from map, so '&' can be done without
    // probe_read, but the next level irqaction * needs a probe read.
    // Do these steps first after reading the map, otherwise some of these
    // pointers may get pushed onto the stack and verifier will fail.
    struct irqaction *action = 0;
    bpf_probe_read(&action, sizeof(action), &(*descp)->action);
    const char **namep = &action->name;
    char *name = 0;
    bpf_probe_read(&name, sizeof(name), namep);
    delta = bpf_ktime_get_ns() - *tsp;

    // store as sum or histogram
    STORE

    start.delete(&pid);
    irqdesc.delete(&pid);
    return 0;
}
"""

# code substitutions
if args.dist:
    bpf_text = bpf_text.replace('STORE',
        'irq_key_t key = {.slot = bpf_log2l(delta)};' +
        'bpf_probe_read(&key.name, sizeof(key.name), name);' +
        'dist.increment(key);')
else:
    bpf_text = bpf_text.replace('STORE',
        'irq_key_t key = {.slot = 0 /* ignore */};' +
        'bpf_probe_read(&key.name, sizeof(key.name), name);' +
        'u64 zero = 0, *vp = dist.lookup_or_init(&key, &zero);' +
        '(*vp) += delta;')
if debug:
    print(bpf_text)

# load BPF program
b = BPF(text=bpf_text)

# these should really use irq:irq_handler_entry/exit tracepoints:
b.attach_kprobe(event="handle_irq_event_percpu", fn_name="trace_start")
b.attach_kretprobe(event="handle_irq_event_percpu", fn_name="trace_completion")

print("Tracing hard irq event time... 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="")

    if args.dist:
        dist.print_log2_hist(label, "hardirq")
    else:
        print("%-26s %11s" % ("HARDIRQ", "TOTAL_" + label))
        for k, v in sorted(dist.items(), key=lambda dist: dist[1].value):
            print("%-26s %11d" % (k.name.decode(), v.value / factor))
    dist.clear()

    countdown -= 1
    if exiting or countdown == 0:
        exit()