harvey/sys/man/3/waitstat

.TH WAITSTAT 3 
.SH NAME
waitstat \- kernel waiting times profiling
.SH SYNOPSIS
.nf
.B bind -a #W /dev
.sp
.B /dev/wsctl
.B /dev/wsdata
.fi
.SH DESCRIPTION
The
.I waitstat
device provides profiling
data for the operating system kernel regarding waiting times (usecs) for locks, mostly.
.PP
The file
.B wsdata
holds one line per program counter where a wait of interest happen. The fields
report the type of waiting event, the program counter, the number of times waiting
did happen there, the maximum waiting time, and the total waiting time.
.PP
The file
.B wsdata
controls profiling for this device.
Writing the string
.B start
to
.B wsctl
begins profiling;
.B stop
terminates it.  The message
.B clear
restarts profiling after zeroing the counts.
.SH EXAMPLE
The following
.IR rc (1)
script runs a test program while profiling the kernel
and reports the results.
.sp
.EX
	bind -a '#W' /dev
	echo start > /dev/wsctl
	runtest
	echo stop > /dev/wsctl
	cat /dev/wsdata
.EE
.SH SOURCE
.B /sys/src/9/port/devws.c
.SH SEE ALSO
.IR kprof (3)