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_IF_BGE 41.Cd options KTR_IF_EM 42.Cd options KTR_IF_START 43.Cd options KTR_IFQ 44.Cd options KTR_IPIQ 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 55.Cd options KTR_CTXSW 56.Sh DESCRIPTION 57The 58.Nm 59facility allows kernel events to be logged while the kernel executes so that 60they can be examined later when debugging. 61The only mandatory option to enable 62.Nm 63is 64.Cd options KTR . 65.Pp 66The 67.Dv KTR_ENTRIES 68option sets the size of the buffer of events. 69It should be a power of two. 70The size of the buffer in the currently running kernel can be found via the 71read-only sysctl 72.Va debug.ktr.entries . 73By default the buffer contains 2048 entries. 74.Pp 75For debugging purposes, the following 76.Nm 77related kernel options exist: 78.Bl -tag -width ".Dv KTR_SPIN_CONTENTION" 79.It Dv KTR_ALL 80turns on all options 81.It Dv KTR_ETHERNET 82cost of 83.Fn ether_input_chain 84and 85.Fn ether_input_dispatch 86.It Dv KTR_IF_BGE 87.Xr bge 4 88interrupts and sent/received packets 89.It Dv KTR_IF_EM 90.Xr em 4 91interrupts, polling and sent/received packets 92.It Dv KTR_IFQ 93classic ifq dequeue/enqueue operation 94.It Dv KTR_IF_START 95running/avoiding/scheduling ifnet.if_start 96.It Dv KTR_IPIQ 97IPI related data (IPI requests, CPU synchronization etc.) 98.It Dv KTR_KERNENTRY 99entry of the kernel from userland (faults, syscalls) 100.It Dv KTR_MEMORY 101.Xr kmalloc 9 102and 103.Xr kfree 9 104events 105.It Dv KTR_POLLING 106.Xr polling 4 107begins and ends 108.It Dv KTR_SERIALIZER 109.Xr serializer 9 110related events 111.It Dv KTR_SPIN_CONTENTION 112.Xr spinlock 9 113contention 114.It Dv KTR_TESTLOG 115IPI performance testing 116.It Dv KTR_TOKENS 117LWKT token related events 118.It Dv KTR_USB_MEMORY 119USB memory allocation 120.It Dv KTR_CTXSW 121context switches 122.El 123.Ss Verbose Mode 124By default, events are only logged to the internal buffer for examination 125later, but if the verbose flag is set then they are dumped to the kernel 126console as well. 127This flag can also be set from the loader via the 128.Va debug.ktr.verbose 129environment variable, or it can be examined and set after booting via the 130.Va debug.ktr.verbose 131sysctl. 132If the flag is set to zero, which is the default, then verbose output is 133disabled. 134If the flag is set to one, then the contents of the log message and the CPU 135number are printed to the kernel console. 136If the flag is greater than one, then the filename and line number of the 137event are output to the console in addition to the log message and the CPU 138number. 139The 140.Dv KTR_VERBOSE 141option enables verbose mode and sets the flag to one. 142.Ss Examining the Events 143The KTR buffer can be examined with 144.Xr ktrdump 8 , 145.Xr gdb 1 146or from within 147.Xr ddb 4 148via the 149.Ic show ktr Op Cm /v 150command. 151This command displays the contents of the trace buffer one page at a time. 152At the 153.Dq Li --more-- 154prompt, the Enter key displays one more entry and prompts again. 155The spacebar displays another page of entries. 156Any other key quits. 157By default the timestamp, filename, and line number are not displayed with 158each log entry. 159If the 160.Cm /v 161modifier is specified, then they are displayed in addition to the normal 162output. 163Note that the events are displayed in reverse chronological order. 164That is, the most recent events are displayed first. 165.Sh SEE ALSO 166.Xr gdb 1 , 167.Xr ddb 4 , 168.Xr ktrdump 8 , 169.Xr ktr 9 170.Sh HISTORY 171The KTR kernel tracing facility first appeared in 172.Bsx 3.0 173and was imported into 174.Fx 5.0 175and 176.Dx 1.1 . 177It was completely rewritten by Matthew Dillon in 178.Dx 1.3 . 179