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.\" 27.Dd September 18, 2012 28.Dt KTR 4 29.Os 30.Sh NAME 31.Nm ktr 32.Nd kernel tracing facility 33.Sh SYNOPSIS 34.Cd options KTR 35.Cd options KTR_ENTRIES=8192 36.Cd options KTR_VERBOSE=1 37.Cd options KTR_ALL 38.Cd options KTR_CTXSW 39.Cd options KTR_DMCRYPT 40.Cd options KTR_ETHERNET 41.\".Cd options KTR_HAMMER 42.Cd options KTR_IF_BGE 43.Cd options KTR_IF_EM 44.Cd options KTR_IF_EMX 45.Cd options KTR_IF_START 46.Cd options KTR_IFQ 47.Cd options KTR_IPIQ 48.Cd options KTR_KERNENTRY 49.Cd options KTR_MEMORY 50.Cd options KTR_SERIALIZER 51.Cd options KTR_SPIN_CONTENTION 52.\".Cd options KTR_TCP 53.Cd options KTR_TESTLOG 54.Cd options KTR_TOKENS 55.Cd options KTR_TSLEEP 56.Cd options KTR_USB_MEMORY 57.Cd options KTR_USCHED_BSD4 58.Cd options KTR_USCHED_DFLY 59.Sh DESCRIPTION 60The 61.Nm 62facility allows kernel events to be logged while the kernel executes so that 63they can be examined later when debugging. 64The only mandatory option to enable 65.Nm 66is 67.Cd options KTR . 68.Pp 69The 70.Dv KTR_ENTRIES 71option sets the size of the buffer of events. 72It must be a power of two. 73The size of the buffer in the currently running kernel can be found via the 74read-only sysctl 75.Va debug.ktr.entries . 76By default the buffer contains 2048 entries. 77.Pp 78For debugging purposes, the following 79.Nm 80related kernel options exist: 81.Bl -tag -width ".Dv KTR_SPIN_CONTENTION" 82.It Dv KTR_ALL 83turns on all options 84.It Dv KTR_CTXSW 85context switches 86.It Dv KTR_DMCRYPT 87read and write strategy paths of 88.Xr dm 4 Ap s 89.Pa crypt 90target 91.It Dv KTR_ETHERNET 92cost of 93.Fn ether_input_pkt 94and 95.Fn ether_dispatch 96.It Dv KTR_IF_BGE 97.Xr bge 4 98interrupts and sent/received packets 99.It Dv KTR_IF_EM 100.Xr em 4 101interrupts and sent/received packets 102.It Dv KTR_IF_EMX 103.Xr emx 4 104interrupts and sent/received packets 105.It Dv KTR_IFQ 106classic ifq dequeue/enqueue operation 107.It Dv KTR_IF_START 108running/avoiding/scheduling ifnet.if_start 109.It Dv KTR_IPIQ 110IPI related data (IPI requests, CPU synchronization etc.) 111.It Dv KTR_KERNENTRY 112entry of the kernel from userland (faults, syscalls) 113.It Dv KTR_MEMORY 114.Xr kmalloc 9 115and 116.Xr kfree 9 117events 118.It Dv KTR_SERIALIZER 119.Xr serializer 9 120related events 121.It Dv KTR_SPIN_CONTENTION 122.Xr spinlock 9 123contention 124.It Dv KTR_TESTLOG 125IPI performance testing 126.It Dv KTR_TOKENS 127LWKT token related events 128.It Dv KTR_TSLEEP 129.Xr tsleep 9 130and 131.Xr wakeup 9 132.It Dv KTR_USB_MEMORY 133USB memory allocation 134.It Dv KTR_USCHED_BSD4 135usched_bsd4 scheduling decisions 136.It Dv KTR_USCHED_DFLY 137usched_dfly scheduling decisions 138.El 139.Ss Verbose Mode 140By default, events are only logged to the internal buffer for examination 141later, but if the verbose flag is set then they are dumped to the kernel 142console as well. 143This flag can also be set from the loader via the 144.Va debug.ktr.verbose 145environment variable, or it can be examined and set after booting via the 146.Va debug.ktr.verbose 147sysctl. 148If the flag is set to zero, which is the default, then verbose output is 149disabled. 150If the flag is set to one, then the contents of the log message and the CPU 151number are printed to the kernel console. 152If the flag is greater than one, then the filename and line number of the 153event are output to the console in addition to the log message and the CPU 154number. 155The 156.Dv KTR_VERBOSE 157option enables verbose mode and sets the flag to one. 158.Ss Examining the Events 159The KTR buffer can be examined with 160.Xr ktrdump 8 , 161.Xr gdb 1 162or from within 163.Xr ddb 4 164via the 165.Ic show ktr Op Cm /v 166command. 167This command displays the contents of the trace buffer one page at a time. 168At the 169.Dq Li --more-- 170prompt, the Enter key displays one more entry and prompts again. 171The spacebar displays another page of entries. 172Any other key quits. 173By default the timestamp, filename, and line number are not displayed with 174each log entry. 175If the 176.Cm /v 177modifier is specified, then they are displayed in addition to the normal 178output. 179Note that the events are displayed in reverse chronological order. 180That is, the most recent events are displayed first. 181.Sh SYSCTL VARIABLES 182.Bl -tag -width ".Va debug.ktr.resynchronize" 183.It Va debug.ktr.*_enable 184A 32 bit mask used to control event logging. 185Each bit corresponds to one or more events depending on the values of the 186.Fa maskbit 187parameters that were passed to the 188.Xr KTR_INFO 9 189calls which declared the events. 190.Pp 191Unless 192.Dv KTR_ALL 193is specified in the kernel configuration, the default is to turn on logging 194for all corresponding events (i.e.\& setting the sysctl to -1). 195.It Va debug.ktr.*_mask 196Read only sysctls (one per event) that show the 197.Va debug.ktr.*_enable 198values corresponding to the events. 199.It Va debug.ktr.resynchronize 200Resynchronize the TSC across all CPUs 10 times per second in an attempt to 201reduce drift errors. 202Note that this is very expensive and therefore the default is 0. 203.El 204.Sh SEE ALSO 205.Xr gdb 1 , 206.Xr ddb 4 , 207.Xr ktrdump 8 , 208.Xr ktr 9 209.Sh HISTORY 210The KTR kernel tracing facility first appeared in 211.Bsx 3.0 212and was imported into 213.Fx 5.0 214and 215.Dx 1.1 . 216It was completely rewritten by Matthew Dillon in 217.Dx 1.3 . 218