Date: Mon, 04 Dec 2006 14:56:49 -0800 (PST) From: John Polstra <jdp@polstra.com> To: current@freebsd.org Subject: LOCK_PROFILING confusion Message-ID: <XFMail.20061204145649.jdp@polstra.com>
next in thread | raw e-mail | index | archive | help
I'm having trouble making sense of the output generated by
LOCK_PROFILING -- in particular, the cnt_hold and cnt_lock stats.
The man page says:
cnt_hold The number of times the lock was held and another
thread attempted to acquire the lock.
cnt_lock The number of times the lock was already held when this
point was reached.
When I enable lock profiling for 30 seconds during heavy network
activity and then look at all of the lines for the sched lock, I see a
lot of non-zero values in the cnt_hold column (including several over
100000 and one over 500000). But all of the values in the cnt_lock
column are 0. How can that be? It seems to me that for a given
lock, the two columns should sum to the same number -- except maybe
for recursive acquisitions, which might increase the cnt_lock numbers
without increasing the cnt_hold numbers. (The descriptions don't say
what happens with recursive acquisitions.)
What am I missing?
John
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?XFMail.20061204145649.jdp>