[Intel-gfx] uABI / Removing DRM_I915_LOW_LEVEL_TRACEPOINTS Kconfig

[Pierre-Loup A. Griffais]

On 12/17/18 6:14 PM, Steven Rostedt wrote:
> On Mon, 17 Dec 2018 18:26:03 -0700
> Michael Sartain <mikesart at fastmail.com> wrote:
> 
>> Ftrace and perf are fantastic, stable, very well known, and documented with
>> ecosystems built around them. AMD already is doing exactly what we are asking
>> for with tracepoints, and Intel has tracepoints that work right now. Please,
>> there must be a way we can enable those and use the current tracing systems
>> without it introducing a stable tracepoint uABI which promises it'll never
>> change until the end of days?
> 
> Would it be helpful if we implemented a way that trace events would not
> show up in the tracefs filesystem unless a specifc kernel command line
> (or module) parameter was supplied?
> 
> That would make for trace events not to be visible by default, but
> allow for the same kernel to make them visible with a simple reboot (or
> module reload). Like adding an option: i915_debug_tracepoints ?
> 
> Or perhaps a sysrq switch?

If something like that was really needed, being able to toggle it (as 
root) without rebooting would be good, otherwise the user experience of 
using such tracing facilities to debug a stutter would suffer quite a bit.

> 
> -- Steve
>