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/man9/ktr.9,v 1.7 2003/09/08 19:57:21 ru Exp $ 26.\" $DragonFly: src/share/man/man9/ktr.9,v 1.1 2004/09/20 20:38:17 eirikn Exp $ 27.\" 28.Dd February 15, 2001 29.Dt KTR 9 30.Os 31.Sh NAME 32.Nm CTR0 , CTR1 , CTR2 , CTR3 , CTR4 , CTR5 , CTR6 33.Nd kernel tracing facility 34.Sh SYNOPSIS 35.In sys/param.h 36.In sys/ktr.h 37.Vt "extern int ktr_cpumask" ; 38.Vt "extern int ktr_entries" ; 39.Vt "extern int ktr_extend" ; 40.Vt "extern int ktr_mask" ; 41.Vt "extern int ktr_verbose" ; 42.Vt "extern struct ktr_entry ktr_buf[]" ; 43.Ft void 44.Fn CTR0 "u_int mask" "char *format" 45.Ft void 46.Fn CTR1 "u_int mask" "char *format" "arg1" 47.Ft void 48.Fn CTR2 "u_int mask" "char *format" "arg1" "arg2" 49.Ft void 50.Fn CTR3 "u_int mask" "char *format" "arg1" "arg2" "arg3" 51.Ft void 52.Fn CTR4 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" 53.Ft void 54.Fn CTR5 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" 55.Ft void 56.Fn CTR6 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" "arg6" 57.Sh DESCRIPTION 58KTR provides a circular buffer of events that can be logged in a 59.Xr printf 9 60style 61fashion. 62These events can then be dumped either via 63.Xr ddb 4 64or 65.Xr gdb 1 . 66.Pp 67Events are created and logged in the kernel via the 68.Dv CTR Ns Ar x 69macros. 70The first parameter is a mask of event types 71.Pq Dv KTR_* 72defined in 73.In sys/ktr.h . 74The event will be logged only if any of the event types specified in 75.Fa mask 76are enabled in the global event mask stored in 77.Va ktr_mask . 78The 79.Fa format 80argument is a 81.Xr printf 9 82style format string used to build the text of the event log message. 83Following the 84.Fa format 85string are zero to five arguments referenced by 86.Fa format . 87Note that the different macros differ only in the number of arguments each 88one takes, as indicated by its name. 89Each event is logged with a timestamp in addition to the log message. 90.Pp 91The 92.Va ktr_entries 93variable contains the number of entries in the 94.Va ktr_buf 95array. 96These variables are mostly useful for post-mortem crash dump tools to locate 97the base of the circular trace buffer and its length. 98.Pp 99The 100.Va ktr_mask 101variable contains the run time mask of events to log. 102.Pp 103The CPU event mask is stored in the 104.Va ktr_cpumask 105variable. 106.Pp 107The 108.Va ktr_verbose 109variable stores the verbose flag that controls whether events are logged to 110the console in addition to the event buffer. 111.Sh EXAMPLES 112This example demonstrates the use of tracepoints at the 113.Dv KTR_PROC 114logging level. 115.Bd -literal -offset indent 116void 117mi_switch() 118{ 119 ... 120 /* 121 * Pick a new current process and record its start time. 122 */ 123 ... 124 CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d, %s)", p, p->p_pid, 125 p->p_comm); 126 ... 127 cpu_switch(); 128 ... 129 CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d, %s)", p, p->p_pid, 130 p->p_comm); 131 ... 132} 133.Ed 134.Sh SEE ALSO 135.Xr ktr 4 136.Sh HISTORY 137The KTR kernel tracing facility first appeared in 138.Bsx 3.0 139and was imported into 140.Fx 5.0 141and 142.Dx 1.1 . 143.Sh BUGS 144Currently there is one global buffer shared among all CPUs. 145It might be profitable at some point in time to use per-CPU buffers instead 146so that if one CPU halts or starts spinning, then the log messages it 147emitted just prior to halting or spinning will not be drowned out by events 148from the other CPUs. 149