- Fix a regression in the irqsoff and wakeup latency tracing
The function graph tracer infrastructure has become generic so that
fprobes and BPF can be based on it. As it use to only handle function
graph tracing, it would always calculate the time the function entered
so that it could then calculate the time it exits and give the length of
time the function executed for. But this is not needed for the other
users (fprobes and BPF) and reading the clock adds a non-negligible
overhead, so the calculation was moved into the function graph tracer
logic.
But the irqsoff and wakeup latency tracers, when the "display-graph"
option was set, would use the function graph tracer to calculate the
times of functions during the latency. The movement of the calltime
calculation made the value zero for these tracers, and the output
no longer showed the length of time of each tracer, but instead the
absolute timestamp of when the function returned (rettime - calltime
where calltime is now zero).
Have the irqsoff and wakeup latency tracers also do the calltime
calculation as the function graph tracer does and report the proper
length of the function timings.
- Update the tracing display to reflect the new preempt lazy model
When the system is configured with preempt lazy, the output of the
trace data would state "unknown" for the current preemption model.
Because the lazy preemption model was just added, make it known
to the tracing subsystem too. This is just a one line change.
- Document multiple function graph having slightly different timings
Now that function graph tracer infrastructure is separate, this also
allows the function graph tracer to run in multiple instances (it wasn't
able to do so before). If two instances ran the function graph tracer and
traced the same functions, the timings for them will be slightly
different because each does their own timings and collects the timestamps
differently. Document this to not have people be confused by it.
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Merge tag 'trace-v6.13-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing fixes from Steven Rostedt:
- Fix a regression in the irqsoff and wakeup latency tracing
The function graph tracer infrastructure has become generic so that
fprobes and BPF can be based on it. As it use to only handle function
graph tracing, it would always calculate the time the function
entered so that it could then calculate the time it exits and give
the length of time the function executed for. But this is not needed
for the other users (fprobes and BPF) and reading the clock adds a
non-negligible overhead, so the calculation was moved into the
function graph tracer logic.
But the irqsoff and wakeup latency tracers, when the "display-graph"
option was set, would use the function graph tracer to calculate the
times of functions during the latency. The movement of the calltime
calculation made the value zero for these tracers, and the output no
longer showed the length of time of each tracer, but instead the
absolute timestamp of when the function returned (rettime - calltime
where calltime is now zero).
Have the irqsoff and wakeup latency tracers also do the calltime
calculation as the function graph tracer does and report the proper
length of the function timings.
- Update the tracing display to reflect the new preempt lazy model
When the system is configured with preempt lazy, the output of the
trace data would state "unknown" for the current preemption model.
Because the lazy preemption model was just added, make it known to
the tracing subsystem too. This is just a one line change.
- Document multiple function graph having slightly different timings
Now that function graph tracer infrastructure is separate, this also
allows the function graph tracer to run in multiple instances (it
wasn't able to do so before). If two instances ran the function graph
tracer and traced the same functions, the timings for them will be
slightly different because each does their own timings and collects
the timestamps differently. Document this to not have people be
confused by it.
* tag 'trace-v6.13-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
ftrace: Document that multiple function_graph tracing may have different times
tracing: Print lazy preemption model
tracing: Fix irqsoff and wakeup latency tracers when using function graph
f692a6c690