Mutex profiling code, conditional on the MUTEX_PROFILING option. Adds the

following sysctl variables:

  debug.mutex.prof.enable	    enable / disable profiling
  debug.mutex.prof.acquisitions	    number of mutex acquisitions recorded
  debug.mutex.prof.records	    number of acquisition points recorded
  debug.mutex.prof.maxrecords	    max number of acquisition points
  debug.mutex.prof.rejected	    number of rejections (due to full table)
  debug.mutex.prof.hashsize	    hash size
  debug.mutex.prof.collisions	    number of hash collisions
  debug.mutex.prof.stats	    profiling statistics

The code records four numbers for each acquisition point (identified by
source file name and line number): longest time held, total time held,
number of non-recursive acquisitions, average time held.  The measurements
are in clock cycles (as returned by get_cyclecount(9)); this may cause
measurements on some SMP systems to be unreliable.  This can probably be
worked around by replacing get_cyclecount(9) by some incarnation of
nanotime(9).

This work was derived from initial patches by eivind.

1 files changed, 3 insertions, 0 deletions

diff --git a/sys/conf/options b/sys/conf/options
index 3800955..2824aa8 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -519,3 +519,6 @@ ED_NO_MIIBUS		opt_ed.h
 
 # Polling device handling
 DEVICE_POLLING		opt_global.h
+
+# Mutex profiling
+MUTEX_PROFILING		opt_global.h