1.\" Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 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. 12.\" 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 23.\" SUCH DAMAGE. 24.\" 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 $ 27.\" 28.Dd October 1, 2008 29.Dt KTR 4 30.Os 31.Sh NAME 32.Nm ktr 33.Nd kernel tracing facility 34.Sh SYNOPSIS 35.Cd options KTR 36.Cd options KTR_ENTRIES=8192 37.Cd options KTR_VERBOSE=1 38.Cd options KTR_ALL 39.Cd options KTR_ETHERNET 40.Cd options KTR_GIANT_CONTENTION 41.Cd options KTR_IF_BGE 42.Cd options KTR_IF_EM 43.Cd options KTR_IF_START 44.Cd options KTR_IFQ 45.Cd options KTR_IPIQ 46.Cd options KTR_KERNENTRY 47.Cd options KTR_MEMORY 48.Cd options KTR_POLLING 49.Cd options KTR_SERIALIZER 50.Cd options KTR_SPIN_CONTENTION 51.\".Cd options KTR_TCP 52.Cd options KTR_TESTLOG 53.Cd options KTR_TOKENS 54.\".Cd options KTR_TSLEEP 55.Cd options KTR_USB_MEMORY 56.Cd options KTR_CTXSW 57.Sh DESCRIPTION 58The 59.Nm 60facility allows kernel events to be logged while the kernel executes so that 61they can be examined later when debugging. 62The only mandatory option to enable 63.Nm 64is 65.Cd options KTR . 66.Pp 67The 68.Dv KTR_ENTRIES 69option sets the size of the buffer of events. 70It should be a power of two. 71The size of the buffer in the currently running kernel can be found via the 72read-only sysctl 73.Va debug.ktr.entries . 74By default the buffer contains 2048 entries. 75.Pp 76For debugging purposes, the following 77.Nm 78related kernel options exist: 79.Bl -tag -width ".Dv KTR_GIANT_CONTENTION" 80.It Dv KTR_ALL 81turns on all options 82.It Dv KTR_ETHERNET 83cost of 84.Fn ether_input_chain 85and 86.Fn ether_input_dispatch 87.It Dv KTR_GIANT_CONTENTION 88contention of the giant lock 89.It Dv KTR_IF_BGE 90.Xr bge 4 91interrupts and sent/received packets 92.It Dv KTR_IF_EM 93.Xr em 4 94interrupts, polling and sent/received packets 95.It Dv KTR_IFQ 96classic ifq dequeue/enqueue operation 97.It Dv KTR_IF_START 98running/avoiding/scheduling ifnet.if_start 99.It Dv KTR_IPIQ 100IPI related data (IPI requests, CPU synchronization etc.) 101.It Dv KTR_KERNENTRY 102entry of the kernel from userland (faults, syscalls) 103.It Dv KTR_MEMORY 104.Xr kmalloc 9 105and 106.Xr kfree 9 107events 108.It Dv KTR_POLLING 109.Xr polling 4 110begins and ends 111.It Dv KTR_SERIALIZER 112.Xr serializer 9 113related events 114.It Dv KTR_SPIN_CONTENTION 115.Xr spinlock 9 116contention 117.It Dv KTR_TESTLOG 118IPI performance testing 119.It Dv KTR_TOKENS 120LWKT token related events 121.It Dv KTR_USB_MEMORY 122USB memory allocation 123.It Dv KTR_CTXSW 124context switches 125.El 126.Ss Verbose Mode 127By default, events are only logged to the internal buffer for examination 128later, but if the verbose flag is set then they are dumped to the kernel 129console as well. 130This flag can also be set from the loader via the 131.Va debug.ktr.verbose 132environment variable, or it can be examined and set after booting via the 133.Va debug.ktr.verbose 134sysctl. 135If the flag is set to zero, which is the default, then verbose output is 136disabled. 137If the flag is set to one, then the contents of the log message and the CPU 138number are printed to the kernel console. 139If the flag is greater than one, then the filename and line number of the 140event are output to the console in addition to the log message and the CPU 141number. 142The 143.Dv KTR_VERBOSE 144option enables verbose mode and sets the flag to one. 145.Ss Examining the Events 146The KTR buffer can be examined with 147.Xr ktrdump 8 , 148.Xr gdb 1 149or from within 150.Xr ddb 4 151via the 152.Ic show ktr Op Cm /v 153command. 154This command displays the contents of the trace buffer one page at a time. 155At the 156.Dq Li --more-- 157prompt, the Enter key displays one more entry and prompts again. 158The spacebar displays another page of entries. 159Any other key quits. 160By default the timestamp, filename, and line number are not displayed with 161each log entry. 162If the 163.Cm /v 164modifier is specified, then they are displayed in addition to the normal 165output. 166Note that the events are displayed in reverse chronological order. 167That is, the most recent events are displayed first. 168.Sh SEE ALSO 169.Xr gdb 1 , 170.Xr ddb 4 , 171.Xr ktrdump 8 , 172.Xr ktr 9 173.Sh HISTORY 174The KTR kernel tracing facility first appeared in 175.Bsx 3.0 176and was imported into 177.Fx 5.0 178and 179.Dx 1.1 . 180It was completely rewritten by Matthew Dillon in 181.Dx 1.3 . 182