Add cli argument to limit run time (iovisor#2428)

If a user is granted sudo access only to btrfsslower.py and not kill or timeout, then user is unable to limit the runtime of btrfsslower.py. The optional cli argument stops execution of program after specified number of seconds passes.

man/man8/btrfsslower.8

@@ -2,7 +2,7 @@
 .SH NAME
 btrfsslower \- Trace slow btrfs file operations, with per-event details.
 .SH SYNOPSIS
-.B btrfsslower [\-h] [\-j] [\-p PID] [min_ms]
+.B btrfsslower [\-h] [\-j] [\-p PID] [min_ms] [\-d DURATION]
 .SH DESCRIPTION
 This tool traces common btrfs file operations: reads, writes, opens, and
 syncs. It measures the time spent in these operations, and prints details
@@ -25,6 +25,9 @@ Trace this PID only.
 .TP
 min_ms
 Minimum I/O latency (duration) to trace, in milliseconds. Default is 10 ms.
+.TP
+\-d DURATION
+Total duration of trace in seconds.
 .SH EXAMPLES
 .TP
 Trace synchronous file reads and writes slower than 10 ms:
@@ -46,6 +49,10 @@ Trace all file reads and writes (warning: the output will be verbose):
 Trace slower than 1 ms, for PID 181 only:
 #
 .B btrfsslower \-p 181 1
+.TP
+Trace for 10 seconds only:
+#
+.B btrfsslower \-d 10
 .SH FIELDS
 .TP
 TIME(s)

tools/btrfsslower.py

@@ -4,7 +4,7 @@
 # btrfsslower Trace slow btrfs operations.
 # For Linux, uses BCC, eBPF.
 #
-# USAGE: btrfsslower [-h] [-j] [-p PID] [min_ms]
+# USAGE: btrfsslower [-h] [-j] [-p PID] [min_ms] [-d DURATION]
 #
 # This script traces common btrfs file operations: reads, writes, opens, and
 # syncs. It measures the time spent in these operations, and prints details
@@ -27,6 +27,7 @@
 from __future__ import print_function
 from bcc import BPF
 import argparse
+from datetime import datetime, timedelta
 from time import strftime
 
 # symbols
@@ -39,6 +40,7 @@
  ./btrfsslower -j 1 # ... 1 ms, parsable output (csv)
  ./btrfsslower 0 # trace all operations (warning: verbose)
  ./btrfsslower -p 185 # trace PID 185 only
+ ./btrfsslower -d 10 # trace for 10 seconds only
 """
 parser = argparse.ArgumentParser(
  description="Trace common btrfs file operations slower than a threshold",
@@ -52,6 +54,8 @@
  help="minimum I/O duration to trace, in ms (default 10)")
 parser.add_argument("--ebpf", action="store_true",
  help=argparse.SUPPRESS)
+parser.add_argument("-d", "--duration",
+ help="total duration of trace in seconds")
 args = parser.parse_args()
 min_ms = int(args.min_ms)
 pid = args.pid
@@ -335,8 +339,9 @@ def print_event(cpu, data, size):
 
 # read events
 b["events"].open_perf_buffer(print_event, page_cnt=64)
-while 1:
+start_time = datetime.now()
+while not args.duration or datetime.now() - start_time < args.duration:
  try:
- b.perf_buffer_poll()
+ b.perf_buffer_poll(timeout=1000)
  except KeyboardInterrupt:
  exit()

tools/btrfsslower_example.txt

@@ -126,7 +126,7 @@ patterns.
 USAGE message:
 
 # ./btrfsslower -h
-usage: btrfsslower [-h] [-j] [-p PID] [min_ms]
+usage: btrfsslower [-h] [-j] [-p PID] [min_ms] [-d DURATION]
 
 Trace common btrfs file operations slower than a threshold
 
@@ -137,10 +137,14 @@ optional arguments:
  -h, --help show this help message and exit
  -j, --csv just print fields: comma-separated values
  -p PID, --pid PID trace this PID only
+ -d DURATION, --duration DURATION
+ total duration of trace in seconds
 
 examples:
  ./btrfsslower # trace operations slower than 10 ms (default)
  ./btrfsslower 1 # trace operations slower than 1 ms
  ./btrfsslower -j 1 # ... 1 ms, parsable output (csv)
  ./btrfsslower 0 # trace all operations (warning: verbose)
  ./btrfsslower -p 185 # trace PID 185 only
+ ./btrfsslower -d 10 # trace for 10 seconds only
+