hardirqs

#!/usr/bin/python
#
# 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, v.value / factor))
	dist.clear()

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