d/freebsd-nq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

mdoc cleanup.

Browse Source 
Submitted by:	ru
This commit is contained in:
Dag-Erling Smørgrav 2004-01-26 12:50:30 +00:00
parent 7735aeb9bb
commit b14fa90f01
1 changed files with 17 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
share/man/man9/MUTEX_PROFILING.9
View File

@ -37,7 +37,7 @@
.Cd "options MUTEX_PROFILING"
.Sh DESCRIPTION
The
.Nm
.Dv MUTEX_PROFILING
kernel option adds support for measuring and reporting mutex use and
contention statistics.
These statistics are collated by acquisition point, these being
@ -65,11 +65,11 @@ In addition, the average hold time is derived from the total hold time
and the number of acquisitions.
.Pp
The
.Nm
.Dv MUTEX_PROFILING
kernel option also adds the following
.Xr sysctl 8
variables to control and monitor the profiling code:
.Bl -tag -width "debug"
.Bl -tag -width indent
.It Va debug.mutex.prof.enable
Enable or disable the mutex profiling code.
This defaults to 0 (off).
@ -77,7 +77,7 @@ This defaults to 0 (off).
The total number of mutex acquisitions recorded.
.It Va debug.mutex.prof.records
The total number of acquisition points recorded.
Note that only active acquisition points (i.e. points that have been
Note that only active acquisition points (i.e., points that have been
reached at least once) are counted.
.It Va debug.mutex.prof.maxrecords
The maximum number of acquisition points the profiling code is capable
@ -96,22 +96,22 @@ The number of hash collisions in the acquisition point hash table.
.It Va debug.mutex.prof.stats
The actual profiling statistics in plain text.
The columns are as follows, from left to right:
.Bl -tag -width "cnt_hold"
.It max
.Bl -tag -width ".Va cnt_hold"
.It Va max
The longest continuous hold time.
.It total
.It Va total
The total (accumulated) hold time.
.It count
.It Va count
The total number of acquisitions.
.It avg
.It Va avg
The average hold time, derived from the total hold time and the number
of acquisitions.
.It cnt_hold
.It Va cnt_hold
The number of times the mutex was contested while being held.
.It cnt_lock
.It Va cnt_lock
The number of times the mutex was already locked when this point was
reached.
.It name
.It Va name
The name of the acquisition point, derived from the source file name
and line number, followed by the name of the mutex in parentheses.
.El
@ -123,6 +123,7 @@ and line number, followed by the name of the mutex in parentheses.
Mutex profiling support appeared in
.Fx 5.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
code was written by
@ -134,14 +135,14 @@ This manual page was written by
.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
.Sh NOTES
The
.Nm
.Dv MUTEX_PROFILING
option increases the size of
.Vt struct mtx ,
.Vt "struct mtx" ,
so a kernel built with that option will not work with modules built
without it.
.Pp
The
.Nm
.Dv MUTEX_PROFILING
option also prevents inlining of the mutex code, which results in a
fairly severe performance penalty.
It should therefore only be enabled on systems where mutex profiling
@ -151,5 +152,5 @@ Measurements are made and stored in nanoseconds using
.Xr nanotime 9 ,
but are presented in microseconds.
This should still be sufficient for the locks one would be most
interested in profiling (those that are held long and / or acquired
interested in profiling (those that are held long and/or acquired
often).