hardirqs: add --count for event counts (iovisor#1460)

man/man8/hardirqs.8

@@ -2,7 +2,7 @@
 .SH NAME
 hardirqs \- Measure hard IRQ (hard interrupt) event time. Uses Linux eBPF/bcc.
 .SH SYNOPSIS
-.B hardirqs [\-h] [\-T] [\-N] [\-d] [interval] [count]
+.B hardirqs [\-h] [\-T] [\-N] [\-C] [\-d] [interval] [outputs]
 .SH DESCRIPTION
 This summarizes the time spent servicing hard IRQs (hard interrupts), and can
 show this time as either totals or histogram distributions. A system-wide
@@ -25,10 +25,13 @@ Print usage message.
 Include timestamps on output.
 .TP
 \-N
-Output in nanoseconds
+Output in nanoseconds.
+.TP
+\-C
+Count events only.
 .TP
 \-d
-Show IRQ time distribution as histograms
+Show IRQ time distribution as histograms.
 .SH EXAMPLES
 .TP
 Sum hard IRQ event time until Ctrl-C:

tools/hardirqs.py

@@ -4,7 +4,7 @@
 # hardirqs Summarize hard IRQ (interrupt) event time.
 # For Linux, uses BCC, eBPF.
 #
-# USAGE: hardirqs [-h] [-T] [-Q] [-m] [-D] [interval] [count]
+# USAGE: hardirqs [-h] [-T] [-N] [-C] [-d] [interval] [outputs]
 #
 # Thanks Amer Ather for help understanding irq behavior.
 #
@@ -33,15 +33,23 @@
  help="include timestamp on output")
 parser.add_argument("-N", "--nanoseconds", action="store_true",
  help="output in nanoseconds")
+parser.add_argument("-C", "--count", action="store_true",
+ help="show event counts instead of timing")
 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,
+parser.add_argument("outputs", nargs="?", default=99999999,
  help="number of outputs")
 args = parser.parse_args()
-countdown = int(args.count)
-if args.nanoseconds:
+countdown = int(args.outputs)
+if args.count and (args.dist or args.nanoseconds):
+ print("The --count option can't be used with time-based options")
+ exit()
+if args.count:
+ factor = 1
+ label = "count"
+elif args.nanoseconds:
  factor = 1
  label = "nsecs"
 else:
@@ -64,6 +72,22 @@
 BPF_HASH(irqdesc, u32, struct irq_desc *);
 BPF_HISTOGRAM(dist, irq_key_t);
 
+// count IRQ
+int count_only(struct pt_regs *ctx, struct irq_desc *desc)
+{
+ u32 pid = bpf_get_current_pid_tgid();
+
+ struct irqaction *action = desc->action;
+ char *name = (char *)action->name;
+
+ 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)++;
+
+ return 0;
+}
+
 // time IRQ
 int trace_start(struct pt_regs *ctx, struct irq_desc *desc)
 {
@@ -119,10 +143,14 @@
 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.")
+if args.count:
+ b.attach_kprobe(event="handle_irq_event_percpu", fn_name="count_only")
+ print("Tracing hard irq events... Hit Ctrl-C to end.")
+else:
+ 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

tools/hardirqs_example.txt

@@ -614,21 +614,55 @@ hardirq = 'resched3'
  2048 -> 4095 : 39 |* |
 
 
+Sometimes you just want counts of events, and don't need the distribution
+of times. You can use the -C or --count option:
+
+# ./hardirqs.py -C
+Tracing hard irq events... Hit Ctrl-C to end.
+^C
+HARDIRQ TOTAL_count
+blkif 2
+callfuncsingle3 8
+callfuncsingle2 10
+callfuncsingle1 18
+resched7 25
+callfuncsingle6 25
+callfuncsingle5 27
+callfuncsingle0 27
+eth0 34
+resched2 40
+resched1 66
+timer7 70
+resched6 71
+resched0 73
+resched5 79
+resched4 90
+timer6 95
+timer4 100
+timer1 109
+timer2 115
+timer0 117
+timer3 123
+resched3 140
+timer5 288
+
+
 USAGE message:
 
 # ./hardirqs -h
-usage: hardirqs [-h] [-T] [-N] [-d] [interval] [count]
+usage: hardirqs [-h] [-T] [-N] [-C] [-d] [interval] [outputs]
 
 Summarize hard irq event time as histograms
 
 positional arguments:
  interval output interval, in seconds
- count  number of outputs
+ outputs number of outputs
 
 optional arguments:
  -h, --help show this help message and exit
  -T, --timestamp include timestamp on output
  -N, --nanoseconds output in nanoseconds
+ -C, --count show event counts instead of timing
  -d, --dist show distributions as histograms
 
 examples: