1 .\" Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org>
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
13 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 .\" $FreeBSD: src/share/man/man4/ktr.4,v 1.9 2003/09/08 19:57:19 ru Exp $
26 .\" $DragonFly: src/share/man/man4/ktr.4,v 1.9 2008/05/15 09:26:14 swildner Exp $
33 .Nd kernel tracing facility
36 .Cd options KTR_ENTRIES=8192
37 .Cd options KTR_VERBOSE=1
39 .Cd options KTR_GIANT_CONTENTION
40 .Cd options KTR_IF_BGE
42 .Cd options KTR_IF_START
45 .Cd options KTR_MEMORY
46 .Cd options KTR_POLLING
47 .Cd options KTR_SERIALIZER
48 .Cd options KTR_SPIN_CONTENTION
49 .\".Cd options KTR_TCP
50 .Cd options KTR_TESTLOG
51 .Cd options KTR_TOKENS
52 .\".Cd options KTR_TSLEEP
53 .Cd options KTR_USB_MEMORY
57 facility allows kernel events to be logged while the kernel executes so that
58 they can be examined later when debugging.
59 The only mandatory option to enable
66 option sets the size of the buffer of events.
67 It should be a power of two.
68 The size of the buffer in the currently running kernel can be found via the
70 .Va debug.ktr.entries .
71 By default the buffer contains 2048 entries.
73 For debugging purposes, the following
75 related kernel options exist:
76 .Bl -tag -width ".Dv KTR_GIANT_CONTENTION"
79 .It Dv KTR_GIANT_CONTENTION
80 contention of the giant lock
83 interrupts and sent/received packets
86 interrupts, polling and sent/received packets
88 classic ifq dequeue/enqueue operation
90 running/avoiding/scheduling ifnet.if_start
92 IPI related data (IPI requests, CPU synchronization etc.)
101 .It Dv KTR_SERIALIZER
104 .It Dv KTR_SPIN_CONTENTION
108 IPI performance testing
110 LWKT token related events
111 .It Dv KTR_USB_MEMORY
112 USB memory allocation
115 By default, events are only logged to the internal buffer for examination
116 later, but if the verbose flag is set then they are dumped to the kernel
118 This flag can also be set from the loader via the
119 .Va debug.ktr.verbose
120 environment variable, or it can be examined and set after booting via the
121 .Va debug.ktr.verbose
123 If the flag is set to zero, which is the default, then verbose output is
125 If the flag is set to one, then the contents of the log message and the CPU
126 number are printed to the kernel console.
127 If the flag is greater than one, then the filename and line number of the
128 event are output to the console in addition to the log message and the CPU
132 option enables verbose mode and sets the flag to one.
133 .Ss Examining the Events
134 The KTR buffer can be examined with
140 .Ic show ktr Op Cm /v
142 This command displays the contents of the trace buffer one page at a time.
145 prompt, the Enter key displays one more entry and prompts again.
146 The spacebar displays another page of entries.
148 By default the timestamp, filename, and line number are not displayed with
152 modifier is specified, then they are displayed in addition to the normal
154 Note that the events are displayed in reverse chronological order.
155 That is, the most recent events are displayed first.
162 The KTR kernel tracing facility first appeared in
164 and was imported into
168 It was completely rewritten by Matthew Dillon in