[PATCH v2] arm64: implement support for static call trampolines

[Steven Rostedt]

On Thu, 29 Oct 2020 12:44:57 +0100
Peter Zijlstra <peterz at infradead.org> wrote:

> IIRC Steve had benchmarks for the ftrace conversion, which is now
> upstream, so that should be simple enough to run.
> 
> Steve, remember how to get numbers out of that?

IIRC, all I did was, before and after the patches run:

	# trace-cmd start -e all

(which is equivalent to "echo 1 > /sys/kernel/tracing/events/enable")

and do:

	# perf stat -r 10 -a ./hackbench 50


Basically running perf stat on hackbench with all events being traced. As
the tracing does indirect jumps without Peter's patches and direct jumps
with the static calls, it gave me a good idea on how much it changed, as
hackbench triggers a lot of trace events when tracing is enabled.

Note, the number of events can change depending on the config. There's a
a few config options that could really stress it (like enabling preempt
enabled/disable tracepoints).

-- Steve