freebsd-dev/share/man/man4/boottrace.4
Mateusz Piotrowski 86e3fb4038 boottrace.4: Document that boottrace is good at tracing one-shot events
Based on an email mhorne@ sent to arch@.

Reviewed by:	debdrup
Differential Revision:	https://reviews.freebsd.org/D34566
2022-07-01 11:09:46 +02:00

223 lines
7.4 KiB
Groff

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.Dd July 1, 2022
.Dt BOOTTRACE 4
.Os
.Sh NAME
.Nm boottrace
.Nd Boot-time, run-time, and shutdown-time tracing facility
.Sh SYNOPSIS
.In sys/boottrace.h
.Sh DESCRIPTION
.Nm
is a kernel-userspace interface for capturing trace events
during system boot and shutdown
.Pq in particular, one-shot events .
.Pp
Event annotations are present in:
.Bl -bullet -compact
.It
the boot and shutdown paths in the
kernel
.It
some key system utilities
.Po
.Xr init 8 ,
.Xr shutdown 8 ,
.Xr reboot 8
.Pc
.It
.Xr rc 8
scripts
.El
.Pp
.Nm
is unconditionally compiled into the kernel and
disabled by default.
.Sh EVENT TABLES
Events are stored in three event tables: boot-time events, run-time events,
and shutdown-time events.
.Bl -column "shutdown-time events" ""
.It Sy Table Name Ta Sy Event Description
.It boot-time events Ta Boot, kernel initialization, and
.Xr rc 8
execution;
.Xo
until
.Xr init 8
transitions into multi-user mode
.Xc
.It run-time events Ta Xo
From when the system has completed booting (including
.Xr rc 8
execution) and
.Xr init 8
transitions to multi-user mode
until the beginning of shutdown procedures
.Xc
.It shutdown-time events Ta Xo
After initialization of a shutdown, a reboot, or a kernel panic
.Xc
.El
.Sh LOADER TUNABLES
Tunables can be set at the
.Xr loader 8
prompt before booting the kernel or stored in
.Xr loader.conf 5 .
.Nm
features the following loader tunables:
.Bl -tag -width indent
.It Va kern.boottrace.dotrace_kernel
Set to
.Ql 1
to enable tracing of kernel events.
Default:
.Ql 1
.Pq enabled .
.It Va kern.boottrace.dotrace_user
Set to
.Ql 1
to enable tracing of userspace events.
Default:
.Ql 1
.Pq enabled .
.El
.Sh SYSCTL VARIABLES
The following variables are available as both
.Xr sysctl 8
variables and
.Xr loader 8
tunables:
.Bl -tag -width indent
.It Va kern.boottrace.boottrace
Create a new trace event and write it to the boot-time table.
.Pp
A new trace event consists of a process name and an event description,
separated by a colon
.Pq Ql \&: .
If the colon is missing or if the provided string for the process name is empty,
the process name is inferred from the invoking process
.Pq which is its executable name .
.It Va kern.boottrace.enabled
Set to
.Ql 1
to enable tracing.
This is a read-only
.Xr sysctl 8
variable.
Default:
.Ql 0
.Pq disabled .
.It Va kern.boottrace.log
Show the events stored in boot-time and run-time
tables.
This
is an opaque
.Xr sysctl 8
variable.
.It Va kern.boottrace.runtrace
Same as
.Va kern.boottrace.boottrace ,
but write to the run-time table.
.It Va kern.boottrace.shuttrace
Same as
.Va kern.boottrace.boottrace ,
but write to the shutdown-time table.
.It Va kern.boottrace.shutdown_trace
Log shutdown-time events to the console before the system halts.
.It Va kern.boottrace.shutdown_trace_threshold
Set a time threshold for logging shutdown-time events in milliseconds.
An event is ignored
if the time difference to the previous event is less than
the threshold value.
Default:
.Ql 0
.Pq logs all events .
.El
.Sh EXAMPLES
Create a new trace event with a process name
.Dq foo
and an event description
.Dq bar
using
.Xr sysctl 8 :
.Bd -literal -offset indent
sysctl kern.boottrace.boottrace="foo:bar"
.Ed
.Pp
Here is a sample output of
.Va kern.boottrace.log
.Po shortened with
.Dq [...]
for readability
.Pc :
.Bd -literal
CPU msecs delta process event PID CPUtime IBlks OBlks
0 44872811 0 kernel sysinit 0x2100001 0 0.00 0 0
0 44872812 1 kernel sysinit 0x2110000 0 0.00 0 0
0 44872812 0 kernel sysinit 0x2140000 0 0.00 0 0
[...]
0 44872817 0 kernel sysinit 0x2800000 0 0.00 0 0
0 44873820 1003 kernel sysinit 0x2880000 0 0.00 0 0
0 44873820 0 kernel sysinit 0x2888000 0 0.00 0 0
[...]
1 44875735 0 kernel sysinit 0xfffffff 0 0.00 0 0
1 44875735 0 swapper mi_startup done 0 0.00 0 0
0 44875750 15 init init(8) starting... 1 0.00 0 0
0 44875751 1 init /etc/rc starting... 1 0.00 0 0
0 44875831 80 boottrace /etc/rc.d/rctl start 26 0.00 0 0
1 44875839 8 boottrace /etc/rc.d/rctl done 26 0.00 2 0
[...]
0 44876446 0 boottrace /etc/rc.d/netif start 390 0.00 0 0
1 44881116 4670 boottrace /etc/rc.d/netif done 390 0.12 34 0
[...]
0 44882866 1 boottrace /etc/rc.d/securelevel start 1679 0.00 0 0
0 44882872 6 boottrace /etc/rc.d/securelevel done 1679 0.00 0 0
1 44882879 7 init /etc/rc finished 1 2.22 743 15
Total measured time: 10068 msecs
CPU msecs delta process event PID CPUtime IBlks OBlks
1 44882880 0 init multi-user start 1 2.22 743 15
0 44918215 35335 kldload hwpmc.ko: sysinit 0xd800000 1698 0.00 0 0
Total measured time: 35335 msecs
.Ed
.Sh SEE ALSO
.Xr tslog 4 ,
.Xr boottrace 8 ,
.Xr sysctl 8
.Sh HISTORY
NetApp created
.Nm
to diagnose slow devices and subsystems.
Once upstreamed,
.Nm
was first publicly released with
.Fx 14.0 .
.Sh AUTHORS
This manual page was written by
.An Mateusz Piotrowski Aq Mt 0mp@FreeBSD.org .