mirror of
https://git.FreeBSD.org/src.git
synced 2024-11-29 08:08:37 +00:00
196 lines
6.3 KiB
Groff
196 lines
6.3 KiB
Groff
.\" Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org>
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd February 16, 2001
|
|
.Dt KTR 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm ktr
|
|
.Nd kernel tracing facility
|
|
.Sh SYNOPSIS
|
|
.Cd options KTR
|
|
.Cd options KTR_ALQ
|
|
.Cd options KTR_COMPILE=(KTR_LOCK|KTR_INTR|KTR_PROC)
|
|
.Cd options KTR_CPUMASK=0x3
|
|
.Cd options KTR_ENTRIES=8192
|
|
.Cd options KTR_MASK=(KTR_INTR|KTR_PROC)
|
|
.Cd options KTR_VERBOSE
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
facility allows kernel events to be logged while the kernel executes so that
|
|
they can be examined later when debugging.
|
|
The only mandatory option to enable
|
|
.Nm
|
|
is
|
|
.Dq Li options KTR .
|
|
.Pp
|
|
The
|
|
.Dv KTR_ENTRIES
|
|
option sets the size of the buffer of events.
|
|
It should be a power of two.
|
|
The size of the buffer in the currently running kernel can be found via the
|
|
read-only sysctl
|
|
.Va debug.ktr.entries .
|
|
By default the buffer contains 1024 entries.
|
|
.Ss Event Masking
|
|
Event levels can be enabled or disabled to trim excessive and overly verbose
|
|
logging.
|
|
First, a mask of events is specified at compile time via the
|
|
.Dv KTR_COMPILE
|
|
option to limit which events are actually compiled into the kernel.
|
|
The default value for this option is for all events to be enabled.
|
|
.Pp
|
|
Secondly, the actual events logged while the kernel runs can be further
|
|
masked via the run time event mask.
|
|
The
|
|
.Dv KTR_MASK
|
|
option sets the default value of the run time event mask.
|
|
The runtime event mask can also be set by the
|
|
.Xr loader 8
|
|
via the
|
|
.Va debug.ktr.mask
|
|
environment variable.
|
|
It can also be examined and set after booting via the
|
|
.Va debug.ktr.mask
|
|
sysctl.
|
|
By default the run time mask is set to log only
|
|
.Dv KTR_GEN
|
|
events.
|
|
The definitions of the event mask bits can be found in
|
|
.In sys/ktr.h .
|
|
.Pp
|
|
Furthermore, there is a CPU event mask whose default value can be changed via
|
|
the
|
|
.Dv KTR_CPUMASK
|
|
option.
|
|
A CPU must have the bit corresponding to its logical id set in this bitmask
|
|
for events that occur on it to be logged.
|
|
This mask can be set by the
|
|
.Xr loader 8
|
|
via the
|
|
.Va debug.ktr.cpumask
|
|
environment variable.
|
|
It can also be examined and set after booting via the
|
|
.Va debug.ktr.cpumask
|
|
sysctl.
|
|
By default events on all CPUs are enabled.
|
|
.Ss Verbose Mode
|
|
By default, events are only logged to the internal buffer for examination
|
|
later, but if the verbose flag is set then they are dumped to the kernel
|
|
console as well.
|
|
This flag can also be set from the loader via the
|
|
.Va debug.ktr.verbose
|
|
environment variable, or it can be examined and set after booting via the
|
|
.Va debug.ktr.verbose
|
|
sysctl.
|
|
If the flag is set to zero, which is the default, then verbose output is
|
|
disabled.
|
|
If the flag is set to one, then the contents of the log message and the CPU
|
|
number are printed to the kernel console.
|
|
If the flag is greater than one, then the filename and line number of the
|
|
event are output to the console in addition to the log message and the CPU
|
|
number.
|
|
The
|
|
.Dv KTR_VERBOSE
|
|
option sets the flag to one.
|
|
.Ss Examining the Events
|
|
The KTR buffer can be examined from within
|
|
.Xr ddb 4
|
|
via the
|
|
.Ic show ktr Op Cm /v
|
|
command.
|
|
This command displays the contents of the trace buffer one page at a time.
|
|
At the
|
|
.Dq Li --more--
|
|
prompt, the Enter key displays one more entry and prompts again.
|
|
The spacebar displays another page of entries.
|
|
Any other key quits.
|
|
By default the timestamp, filename, and line number are not displayed with
|
|
each log entry.
|
|
If the
|
|
.Cm /v
|
|
modifier is specified, then they are displayed in addition to the normal
|
|
output.
|
|
Note that the events are displayed in reverse chronological order.
|
|
That is, the most recent events are displayed first.
|
|
.Ss Logging ktr to Disk
|
|
The
|
|
.Dv KTR_ALQ
|
|
option can be used to log
|
|
.Nm
|
|
entries to disk for post analysis using the
|
|
.Xr ktrdump 8
|
|
utility.
|
|
Due to the potentially high volume of trace messages the trace mask should be
|
|
selected carefully.
|
|
This feature is configured through a group of sysctls.
|
|
.Bl -tag -width ".Va debug.ktr.alq_enable"
|
|
.It Va debug.ktr.alq_file
|
|
displays or sets the file that
|
|
.Nm
|
|
will log to.
|
|
By default its value is
|
|
.Pa /tmp/ktr.out .
|
|
If the file name is changed while
|
|
.Nm
|
|
is enabled it will not take effect until
|
|
the next invocation.
|
|
.It Va debug.ktr.alq_enable
|
|
enables logging of
|
|
.Nm
|
|
entries to disk if it is set to one.
|
|
Setting this to 0 will terminate logging.
|
|
.It Va debug.ktr.alq_max
|
|
is the maximum number of entries that will be recorded to disk, or 0 for
|
|
infinite.
|
|
This is helpful for limiting the number of particularly high frequency entries
|
|
that are recorded.
|
|
.It Va debug.ktr.alq_depth
|
|
determines the number of entries in the write buffer.
|
|
This is the buffer that holds entries before they are written to disk and
|
|
defaults to the value of the
|
|
.Dv KTR_ENTRIES
|
|
option.
|
|
.It Va debug.ktr.alq_failed
|
|
records the number of times we failed to write an entry due to overflowing the
|
|
write buffer.
|
|
This may happen if the frequency of the logged
|
|
.Nm
|
|
messages outpaces the depth
|
|
of the queue.
|
|
.It Va debug.ktr.alq_cnt
|
|
records the number of entries that have currently been written to disk.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr ktrdump 8 ,
|
|
.Xr ktr 9
|
|
.Sh HISTORY
|
|
The KTR kernel tracing facility first appeared in
|
|
.Bsx 3.0
|
|
and was imported into
|
|
.Fx 5.0 .
|