Optionally produce stats on syscall latency

Time spent in system time is not useful where a syscall depends on some
non-CPU resource, eg. typically open() or stat() to a network drive.

This patch adds a new flag (-w) to produce a summary of the time
difference between beginning and end of the system call (ie. latency)

This functionality has been useful to profile slow processes that
are not CPU-bound.

Signed-off-by: Mark Hills <mark.hills@framestore.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/strace.1 b/strace.1
index 6ca4bdaa0..4d26be52b 100644
--- a/strace.1
+++ b/strace.1
@@ -290,6 +290,10 @@ of seconds since the epoch.
 Show the time spent in system calls. This records the time
 difference between the beginning and the end of each system call.
 .TP
+.B \-w
+Summarise the time difference between the beginning and end of
+each system call. The default is to summarise the system time.
+.TP
 .B \-v
 Print unabbreviated versions of environment, stat, termios, etc.
 calls.  These structures are very common in calls and so the default