Adding a couple of optional parameters to tcpconnlat.

1. Adding `-m` and `-u` parameters for filtering tcp connects with greater the specified minimum latency.
2. Adding -v option to print out the bpf program. This is helpful for debugging and is a bit more consistent with some of the other bpf tools.

The latency check is only added if `-u` or `-m` have been set to greater than 0.

tools/tcpconnlat.py

@@ -24,6 +24,8 @@
 # arguments
 examples = """examples:
  ./tcpconnlat # trace all TCP connect()s
+ ./tcpconnlat -m 1 # only show results slower than 1 ms
+ ./tcpconnlat -u 100 # only show results slower than 100 microseconds
  ./tcpconnlat -t # include timestamps
  ./tcpconnlat -p 181 # only trace PID 181
 """
@@ -35,7 +37,21 @@
  help="include timestamp on output")
 parser.add_argument("-p", "--pid",
  help="trace this PID only")
+parser.add_argument("-m", "--min-ms", type=float, dest="min_ms",
+ help="minimum latency filter (ms)")
+parser.add_argument("-u", "--min-us", type=float, dest="min_us",
+ help="minimum latency filter (us)")
+parser.add_argument("-v", "--verbose", action="store_true",
+ help="print the BPF program for debugging purposes")
 args = parser.parse_args()
+
+if args.min_ms:
+ duration_us = int(args.min_ms * 1000)
+elif args.min_us:
+ duration_us = int(args.min_us)
+else:
+ duration_us = 0 # default is show all
+
 debug = 0
 
 # define BPF program
@@ -104,9 +120,18 @@
  if (infop == 0) {
  return 0; // missed entry or filtered
  }
+
  u64 ts = infop->ts;
  u64 now = bpf_ktime_get_ns();
 
+ u64 delta_us = (now - ts) / 1000ul;
+
+#ifdef MIN_LATENCY
+ if ( delta_us < DURATION_US ) {
+ return 0; // connect latency is below latency filter minimum
+ }
+#endif
+
  // pull in details
  u16 family = 0, dport = 0;
  family = skp->__sk_common.skc_family;
@@ -142,13 +167,17 @@
 }
 """
 
+if duration_us > 0:
+ bpf_text = "#define MIN_LATENCY\n" + bpf_text
+ bpf_text = bpf_text.replace('DURATION_US', str(duration_us))
+
 # code substitutions
 if args.pid:
  bpf_text = bpf_text.replace('FILTER',
  'if (pid != %s) { return 0; }' % args.pid)
 else:
  bpf_text = bpf_text.replace('FILTER', '')
-if debug:
+if debug or args.verbose:
  print(bpf_text)
 
 # initialize BPF