Hi Jon,
Jon Haslam wrote:
Hi Max,
From taking a quick look at plockstat.c, the nsec column is a sum
of the number of nanoseconds that a mutex is held. Count is a count
of the number of times the mutex is acquired. According to this
output, a malloc lock is aquired and released
approximately 4 million times, but the total time spent holding the lock
is approximately 4000 nsecs. So, on average, the lock is held for
4000nsec/4000000
or .001 nsecs!!! I did not think my machine was so fast! If I use
the plockstat
provider directly with dtrace, I get reasonable results.
So, is my arithmetic wrong, or is there another explanation?
I think you're just misreading the source. The 'nsec' column is
the average duration of the event in nanoseconds. The plockstat(1M)
man page could probably do with a "display formats" section similar
to what lockstat(1M) has. I'll file a doc bug.
Thanks. You are right. I saw the sum() aggregating function and assumed
that is what was displayed. When the do the display, the divide the sum
value
by the count value to get the average.
max
Jon.
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