TSLOG(4) FreeBSD Kernel Interfaces Manual TSLOG(4)
NAME
tslog - Boot-time event tracing facility
SYNOPSIS
To compile this boot-time event tracing facility into the kernel, place
the following line in the kernel configuration file:
option TSLOG
DESCRIPTION
tslog is a boot-time event tracing facility. It is suitable for tracing
recursive events based on function entries and exits. Its purpose is to
ease pinpointing and reducing the overall FreeBSD boot time by generating
detailed timing information.
tslog is able to trace the boot loader, kernel initialization, and
userland processes.
In userland, it records the following details for each process ID:
- The timestamp of the fork(2) which creates the given process ID and
the parent process ID.
- The path passed to execve(2), if any.
- The first path resolved by namei(9), if any.
- The timestamp of the exit(3) which terminates the process.
SYSCTL VARIABLES
The following sysctl(8) variables are available:
debug.tslog
Dump the tslog buffer of recorded loader and kernel event
timestamps.
debug.tslog_user
Dump the tslog buffer of recorded userland event timestamps.
FLAMEGRAPHS
The tslog buffer dumps can be used to generate flamegraphs of the FreeBSD
boot process for visual analysis. See
https://github.com/cperciva/freebsd-boot-profiling for more information.
SEE ALSO
dtrace(1), boottrace(4), ktr(4)
HISTORY
tslog first appeared in FreeBSD 12.0. Support for tracing boot loaders
and userland process was added in FreeBSD 13.2.
TSLOG vs. Boottrace
tslog is oriented towards system developers while boottrace(4) is meant
to be easy to use by system administrators. Both faciliities provide an
overview of timing and resource usage of the boot process.
TSLOG vs. DTrace
dtrace(1) is not always the right tool for profiling early kernel
initialization. The reason is it requires some kernel subroutines which
are not yet available early in the boot process, e.g.: traps, memory
allocation, or thread scheduling. tslog depends on fewer kernel
subroutines than dtrace(1) and because of that can trace early kernel
initialization.
TSLOG vs. KTR
ktr(4) has a couple of limitations which prevent it from being able to
run at the start of the boot process. In contrast, tslog is designed for
logging timestamped events for boot profiling.
AUTHORS
tslog was written by Colin Percival <
[email protected]>.
This manual page was written by Mateusz Piotrowski <
[email protected]>.
FreeBSD 14.1-RELEASE-p8 June 1, 2022 FreeBSD 14.1-RELEASE-p8