.\" Copyright (c) 2001 John H. Baldwin .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD: src/share/man/man4/ktr.4,v 1.9 2003/09/08 19:57:19 ru Exp $ .\" .Dd July 17, 2011 .Dt KTR 4 .Os .Sh NAME .Nm ktr .Nd kernel tracing facility .Sh SYNOPSIS .Cd options KTR .Cd options KTR_ENTRIES=8192 .Cd options KTR_VERBOSE=1 .Cd options KTR_ALL .Cd options KTR_CTXSW .Cd options KTR_DMCRYPT .Cd options KTR_ETHERNET .\".Cd options KTR_HAMMER .Cd options KTR_IF_BGE .Cd options KTR_IF_EM .Cd options KTR_IF_EMX .Cd options KTR_IF_START .Cd options KTR_IFQ .Cd options KTR_IPIQ .Cd options KTR_KERNENTRY .Cd options KTR_MEMORY .Cd options KTR_POLLING .Cd options KTR_SERIALIZER .Cd options KTR_SPIN_CONTENTION .\".Cd options KTR_TCP .Cd options KTR_TESTLOG .Cd options KTR_TOKENS .\".Cd options KTR_TSLEEP .Cd options KTR_USB_MEMORY .Sh DESCRIPTION The .Nm facility allows kernel events to be logged while the kernel executes so that they can be examined later when debugging. The only mandatory option to enable .Nm is .Cd options KTR . .Pp The .Dv KTR_ENTRIES option sets the size of the buffer of events. It must be a power of two. The size of the buffer in the currently running kernel can be found via the read-only sysctl .Va debug.ktr.entries . By default the buffer contains 2048 entries. .Pp For debugging purposes, the following .Nm related kernel options exist: .Bl -tag -width ".Dv KTR_SPIN_CONTENTION" .It Dv KTR_ALL turns on all options .It Dv KTR_CTXSW context switches .It Dv KTR_DMCRYPT read and write strategy paths of .Xr dm 4 Ap s .Pa crypt target .It Dv KTR_ETHERNET cost of .Fn ether_input_chain and .Fn ether_input_dispatch .It Dv KTR_IF_BGE .Xr bge 4 interrupts and sent/received packets .It Dv KTR_IF_EM .Xr em 4 interrupts and sent/received packets .It Dv KTR_IF_EMX .Xr emx 4 interrupts and sent/received packets .It Dv KTR_IFQ classic ifq dequeue/enqueue operation .It Dv KTR_IF_START running/avoiding/scheduling ifnet.if_start .It Dv KTR_IPIQ IPI related data (IPI requests, CPU synchronization etc.) .It Dv KTR_KERNENTRY entry of the kernel from userland (faults, syscalls) .It Dv KTR_MEMORY .Xr kmalloc 9 and .Xr kfree 9 events .It Dv KTR_POLLING .Xr polling 4 begins and ends .It Dv KTR_SERIALIZER .Xr serializer 9 related events .It Dv KTR_SPIN_CONTENTION .Xr spinlock 9 contention .It Dv KTR_TESTLOG IPI performance testing .It Dv KTR_TOKENS LWKT token related events .It Dv KTR_USB_MEMORY USB memory allocation .El .Ss Verbose Mode By default, events are only logged to the internal buffer for examination later, but if the verbose flag is set then they are dumped to the kernel console as well. This flag can also be set from the loader via the .Va debug.ktr.verbose environment variable, or it can be examined and set after booting via the .Va debug.ktr.verbose sysctl. If the flag is set to zero, which is the default, then verbose output is disabled. If the flag is set to one, then the contents of the log message and the CPU number are printed to the kernel console. If the flag is greater than one, then the filename and line number of the event are output to the console in addition to the log message and the CPU number. The .Dv KTR_VERBOSE option enables verbose mode and sets the flag to one. .Ss Examining the Events The KTR buffer can be examined with .Xr ktrdump 8 , .Xr gdb 1 or from within .Xr ddb 4 via the .Ic show ktr Op Cm /v command. This command displays the contents of the trace buffer one page at a time. At the .Dq Li --more-- prompt, the Enter key displays one more entry and prompts again. The spacebar displays another page of entries. Any other key quits. By default the timestamp, filename, and line number are not displayed with each log entry. If the .Cm /v modifier is specified, then they are displayed in addition to the normal output. Note that the events are displayed in reverse chronological order. That is, the most recent events are displayed first. .Sh SYSCTL VARIABLES .Bl -tag -width ".Va debug.ktr.resynchronize" .It Va debug.ktr.*_enable A 32 bit mask used to control event logging. Each bit corresponds to one or more events depending on the values of the .Fa maskbit parameters that were passed to the .Xr KTR_INFO 9 calls which declared the events. .Pp Unless .Dv KTR_ALL is specified in the kernel configuration, the default is to turn on logging for all corresponding events (i.e.\& setting the sysctl to -1). .It Va debug.ktr.*_mask Read only sysctls (one per event) that show the .Va debug.ktr.*_enable values corresponding to the events. .It Va debug.ktr.resynchronize Resynchronize the TSC across all CPUs 10 times per second in an attempt to reduce drift errors. Note that this is very expensive and therefore the default is 0. .El .Sh SEE ALSO .Xr gdb 1 , .Xr ddb 4 , .Xr ktrdump 8 , .Xr ktr 9 .Sh HISTORY The KTR kernel tracing facility first appeared in .Bsx 3.0 and was imported into .Fx 5.0 and .Dx 1.1 . It was completely rewritten by Matthew Dillon in .Dx 1.3 .