tracing/osnoise: Add option to align tlat threads

Add an option called TIMERLAT_ALIGN to osnoise/options, together with a
corresponding setting osnoise/timerlat_align_us.

This option sets the alignment of wakeup times between different
timerlat threads, similarly to cyclictest's -A/--aligned option. If
TIMERLAT_ALIGN is set, the first thread that reaches the first cycle
records its first wake-up time. Each following thread sets its first
wake-up time to a fixed offset from the recorded time, and increments
it by the same offset.

Example:

osnoise/timerlat_period is set to 1000, osnoise/timerlat_align_us is
set to 20. There are four threads, on CPUs 1 to 4.

- CPU 4 enters first cycle first. The current time is 20000us, so
the wake-up of the first cycle is set to 21000us. This time is recorded.
- CPU 2 enter first cycle next. It reads the recorded time, increments
it to 21020us, and uses this value as its own wake-up time for the first
cycle.
- CPU 3 enters first cycle next. It reads the recorded time, increments
it to 21040 us, and uses the value as its own wake-up time.
- CPU 1 proceeds analogically.

In each next cycle, the wake-up time (called "absolute period" in
timerlat code) is incremented by the (relative) period of 1000us. Thus,
the wake-ups in the following cycles (provided the times are reached and
not in the past) will be as follows:

CPU 1		CPU 2		CPU 3	 	CPU 4
21080us		21020us		21040us		21000us
22080us		22020us		22040us		22000us
...		...		...		...

Even if any cycle is skipped due to e.g. the first cycle calculation
happening later, the alignment stays in place.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Cc: Costa Shulyupin <costa.shul@redhat.com>
Link: https://patch.msgid.link/20260416115942.544032-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Reviewed-by: Wander Lairson Costa <wander@redhat.com>
Reviewed-by: Crystal Wood <crwood@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

0 files changed, 0 insertions, 0 deletions