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 either via 60.Xr ddb 4 61or 62.Xr gdb 1 . 63.Pp 64Events are created and logged in the kernel via the 65.Dv CTR Ns Ar x 66macros. 67The first parameter is a mask of event types 68.Pq Dv KTR_* 69defined in 70.Aq Pa sys/ktr.h . 71The event will be logged only if any of the event types specified in 72.Fa mask 73are enabled in the global event mask stored in 74.Va ktr_mask . 75The 76.Fa format 77argument is a 78.Xr printf 9 79style format string used to build the text of the event log message. 80Following the 81.Fa format 82string are zero to five arguments referenced by 83.Fa format . 84Note that the different macros differ only in the number of arguments each 85one takes, as indicated by its name. 86Each event is logged with a timestamp in addition to the log message. 87.Pp 88The 89.Va ktr_entries 90variable contains the number of entries in the 91.Va ktr_buf 92array. 93These variables are mostly useful for post-mortem crash dump tools to locate 94the base of the circular trace buffer and its length. 95.Pp 96The 97.Va ktr_mask 98variable contains the run time mask of events to log. 99.Pp 100The CPU event mask is stored in the 101.Va ktr_cpumask 102variable. 103.Pp 104The 105.Va ktr_verbose 106variable stores the verbose flag that controls whether events are logged to 107the console in addition to the event buffer. 108.Sh EXAMPLES 109This example demonstrates the use of tracepoints at the 110.Dv KTR_PROC 111logging level. 112.Bd -literal -offset indent 113void 114mi_switch() 115{ 116 ... 117 /* 118 * Pick a new current process and record its start time. 119 */ 120 ... 121 CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d, %s)", p, p->p_pid, 122 p->p_comm); 123 ... 124 cpu_switch(); 125 ... 126 CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d, %s)", p, p->p_pid, 127 p->p_comm); 128 ... 129} 130.Ed 131.Sh SEE ALSO 132.Xr ktr 4 , 133.Xr ktrdump 8 134.Sh HISTORY 135The KTR kernel tracing facility first appeared in 136.Bsx 3.0 137and was imported into 138.Fx 5.0 . 139.Sh BUGS 140Currently there is one global buffer shared among all CPUs. 141It might be profitable at some point in time to use per-CPU buffers instead 142so that if one CPU halts or starts spinning, then the log messages it 143emitted just prior to halting or spinning will not be drowned out by events 144from the other CPUs. 145