avg
Stores the arithmetic average of the specified expressions in an aggregation.
void avg(expr)
The avg
function is an aggregation function to return the arithmetic
average for a specified D expression.
Example 7-2 How to use avg to display the average time that processes spend in the system write call
The example stores the timestamp for the syscall::write:entry
probe fires
and then subtracts this value from the timestamp when the
syscall::write:return
fires. The average time is calculated based on the
time difference between the two probes and stored in an aggregation so that it can be
updated for each process that runs. When the program exits, the aggregated average timestamp
value is displayed for each process identified by the built-in variable
execname
.
syscall::write:entry
{
self->ts = timestamp;
}
syscall::write:return
/self->ts/
{
@time[execname] = avg(timestamp - self->ts);
self->ts = 0;
}
Output similar to the following is displayed when the program exits:
gnome-session 8260
udisks-part-id 9279
gnome-terminal 9378
lsof 14903
ip 15075
date 15371
...
ps 91792
sestatus 98374
pstree 102566
udisks-daemon 250405
gconfd-2 17880523
cat 59752284