1 .\" Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org>
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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 1.11 2008/10/01 10:53:48 swildner Exp $
33 .Nd kernel tracing facility
36 .Cd options KTR_ENTRIES=8192
37 .Cd options KTR_VERBOSE=1
39 .Cd options KTR_ETHERNET
40 .Cd options KTR_IF_BGE
42 .Cd options KTR_IF_START
45 .Cd options KTR_KERNENTRY
46 .Cd options KTR_MEMORY
47 .Cd options KTR_POLLING
48 .Cd options KTR_SERIALIZER
49 .Cd options KTR_SPIN_CONTENTION
50 .\".Cd options KTR_TCP
51 .Cd options KTR_TESTLOG
52 .Cd options KTR_TOKENS
53 .\".Cd options KTR_TSLEEP
54 .Cd options KTR_USB_MEMORY
59 facility allows kernel events to be logged while the kernel executes so that
60 they can be examined later when debugging.
61 The only mandatory option to enable
68 option sets the size of the buffer of events.
69 It should be a power of two.
70 The size of the buffer in the currently running kernel can be found via the
72 .Va debug.ktr.entries .
73 By default the buffer contains 2048 entries.
75 For debugging purposes, the following
77 related kernel options exist:
78 .Bl -tag -width ".Dv KTR_SPIN_CONTENTION"
85 .Fn ether_input_dispatch
88 interrupts and sent/received packets
91 interrupts, polling and sent/received packets
93 classic ifq dequeue/enqueue operation
95 running/avoiding/scheduling ifnet.if_start
97 IPI related data (IPI requests, CPU synchronization etc.)
99 entry of the kernel from userland (faults, syscalls)
108 .It Dv KTR_SERIALIZER
111 .It Dv KTR_SPIN_CONTENTION
115 IPI performance testing
117 LWKT token related events
118 .It Dv KTR_USB_MEMORY
119 USB memory allocation
124 By default, events are only logged to the internal buffer for examination
125 later, but if the verbose flag is set then they are dumped to the kernel
127 This flag can also be set from the loader via the
128 .Va debug.ktr.verbose
129 environment variable, or it can be examined and set after booting via the
130 .Va debug.ktr.verbose
132 If the flag is set to zero, which is the default, then verbose output is
134 If the flag is set to one, then the contents of the log message and the CPU
135 number are printed to the kernel console.
136 If the flag is greater than one, then the filename and line number of the
137 event are output to the console in addition to the log message and the CPU
141 option enables verbose mode and sets the flag to one.
142 .Ss Examining the Events
143 The KTR buffer can be examined with
149 .Ic show ktr Op Cm /v
151 This command displays the contents of the trace buffer one page at a time.
154 prompt, the Enter key displays one more entry and prompts again.
155 The spacebar displays another page of entries.
157 By default the timestamp, filename, and line number are not displayed with
161 modifier is specified, then they are displayed in addition to the normal
163 Note that the events are displayed in reverse chronological order.
164 That is, the most recent events are displayed first.
171 The KTR kernel tracing facility first appeared in
173 and was imported into
177 It was completely rewritten by Matthew Dillon in