hi Mathieu,
* Mathieu Desnoyers <[email protected]> wrote:
> Hi,
>
> Here is the architecture dependent instrumentation for LTTng. [...]
A fundamental observation about markers, and i raised this point many
many months ago already, so it might sound repetitive, but i'm unsure
wether it's addressed. Documentation/markers.txt still says:
| * Purpose of markers
|
| A marker placed in code provides a hook to call a function (probe)
| that you can provide at runtime. A marker can be "on" (a probe is
| connected to it) or "off" (no probe is attached). When a marker is
| "off" it has no effect, except for adding a tiny time penalty
| (checking a condition for a branch) and space penalty (adding a few
| bytes for the function call at the end of the instrumented function
| and adds a data structure in a separate section).
could you please eliminate the checking of the flag, and insert a pure
NOP sequence by default (no extra branches), which is then patched in
with a function call instruction sequence, when the trace point is
turned on? (on architectures that have code patching infrastructure -
such as x86)
Ingo
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