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.\" $FreeBSD$ 26.\" 27.Dd February 15, 2001 28.Dt KTR 9 29.Os 30.Sh NAME 31.Nm CTR0 , CTR1 , CTR2 , CTR3 , CTR4 , CTR5 32.Nd kernel tracing facility 33.Sh SYNOPSIS 34.In sys/param.h 35.In sys/ktr.h 36.Vt "extern int ktr_cpumask" ; 37.Vt "extern int ktr_entries" ; 38.Vt "extern int ktr_extend" ; 39.Vt "extern int ktr_mask" ; 40.Vt "extern int ktr_verbose" ; 41.Vt "extern struct ktr_entry ktr_buf[]" ; 42.Ft void 43.Fn CTR0 "u_int mask" "char *format" 44.Ft void 45.Fn CTR1 "u_int mask" "char *format" "arg1" 46.Ft void 47.Fn CTR2 "u_int mask" "char *format" "arg1" "arg2" 48.Ft void 49.Fn CTR3 "u_int mask" "char *format" "arg1" "arg2" "arg3" 50.Ft void 51.Fn CTR4 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" 52.Ft void 53.Fn CTR5 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" 54.Sh DESCRIPTION 55KTR provides a circular buffer of events that can be logged in a 56.Xr printf 9 57style 58fashion. 59These events can then be dumped with 60.Xr ddb 4 , 61.Xr gdb 1 62or 63.Xr ktrdump 8 . 64.Pp 65Events are created and logged in the kernel via the 66.Dv CTR Ns Ar x 67macros. 68The first parameter is a mask of event types 69.Pq Dv KTR_* 70defined in 71.In sys/ktr.h . 72The event will be logged only if any of the event types specified in 73.Fa mask 74are enabled in the global event mask stored in 75.Va ktr_mask . 76The 77.Fa format 78argument is a 79.Xr printf 9 80style format string used to build the text of the event log message. 81Following the 82.Fa format 83string are zero to five arguments referenced by 84.Fa format . 85Note that the different macros differ only in the number of arguments each 86one takes, as indicated by its name. 87Each event is logged with a timestamp in addition to the log message. 88.Pp 89The 90.Va ktr_entries 91variable contains the number of entries in the 92.Va ktr_buf 93array. 94These variables are mostly useful for post-mortem crash dump tools to locate 95the base of the circular trace buffer and its length. 96.Pp 97The 98.Va ktr_mask 99variable contains the run time mask of events to log. 100.Pp 101The CPU event mask is stored in the 102.Va ktr_cpumask 103variable. 104.Pp 105The 106.Va ktr_verbose 107variable stores the verbose flag that controls whether events are logged to 108the console in addition to the event buffer. 109.Sh EXAMPLES 110This example demonstrates the use of tracepoints at the 111.Dv KTR_PROC 112logging level. 113.Bd -literal 114void 115mi_switch() 116{ 117 ... 118 /* 119 * Pick a new current process and record its start time. 120 */ 121 ... 122 CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d, %s)", p, p->p_pid, 123 p->p_comm); 124 ... 125 cpu_switch(); 126 ... 127 CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d, %s)", p, p->p_pid, 128 p->p_comm); 129 ... 130} 131.Ed 132.Sh SEE ALSO 133.Xr ktr 4 , 134.Xr ktrdump 8 135.Sh HISTORY 136The KTR kernel tracing facility first appeared in 137.Bsx 3.0 138and was imported into 139.Fx 5.0 . 140.Sh BUGS 141Currently there is one global buffer shared among all CPUs. 142It might be profitable at some point in time to use per-CPU buffers instead 143so that if one CPU halts or starts spinning, then the log messages it 144emitted just prior to halting or spinning will not be drowned out by events 145from the other CPUs. 146