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Examples of accept2close-nd.stp, the Linux SystemTap version.


This shows accepted socket lifespans, by measuring the time from syscall
accept() to close() on the same file descriptor. Sessions are printed as they
occur, and a histogram summary is printed at the end. For example:

# ./accept2close-nd.stp
TIME                     PID    COMM           FD   DURATION
Sat Jan 31 05:31:14 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   2 ms
Sat Jan 31 05:31:15 2015 29042  node           11   3 ms
Sat Jan 31 05:31:15 2015 29042  node           11   2 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
Sat Jan 31 05:31:15 2015 29042  node           11   1 ms
[...]
Duration (ns):
   value |-------------------------------------------------- count
  131072 |                                                     0
  262144 |                                                     0
  524288 |                                                     1
 1048576 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@     138
 2097152 |@@                                                   6
 4194304 |                                                     1
 8388608 |                                                     0
16777216 |                                                     0

Most of these sessions were between 1 and 2 milliseconds in lifespan.

The socket lifespan is expected to represent the time taken by a server to
respond to a request. This time may include cycles on-CPU, and cycles off-CPU
blocked on another resource. Note that HTTP keep-alive sessions may have long
durations which process multiple requests.


accept2close-nd.stp accepts an optional argument: a minimum lifespan threshold
in milliseconds. For example, socket sessions that are 5 milliseconds and
longer:

# ./accept2close-nd.stp 5
Only tracing events slower than 5 ms.
TIME                     PID    COMM           FD   DURATION
Sat Jan 31 05:36:23 2015 5236   node           11   5 ms
Sat Jan 31 05:37:39 2015 5236   node           11   5 ms
Sat Jan 31 05:37:50 2015 5236   node           11   9 ms
Sat Jan 31 05:38:09 2015 5236   node           11   7 ms
^C
Duration (ns):
   value |-------------------------------------------------- count
 1048576 |                                                   0
 2097152 |                                                   0
 4194304 |@@@                                                3
 8388608 |@                                                  1
16777216 |                                                   0
33554432 |                                                   0