Re: [PATCH] tracing/events: Expand ring buffer for in-kernel event enables

[manjunath.b.patil@oracle.com]

On 6/2/26 6:00 AM, Steven Rostedt wrote:
> On Mon,  1 Jun 2026 16:24:43 -0700
> Manjunath Patil <manjunath.b.patil@oracle.com> wrote:
> 
>> Ftrace keeps trace arrays at a boot-minimum ring-buffer size until
>> tracing is used. Tracefs event-enable paths already call
>> tracing_update_buffers() before enabling events, but the exported
>> in-kernel helpers trace_set_clr_event() and trace_array_set_clr_event()
>> directly enable events through __ftrace_set_clr_event().
>>
>> This can leave events enabled by in-kernel users recording into the tiny
>> boot-minimum buffer instead of the configured default-sized buffer. Any
>> caller that enables events through these exported helpers observes
>> different buffer-expansion behavior than a userspace tracefs event enable.
>>
>> Expand the relevant trace array before enabling events through the
>> exported in-kernel helpers, matching the tracefs event-enable behavior.
>> Disabling events remains unchanged.
> 
> The above explains everything correctly, but you left out what needs this?
> 
> Internal code should not be using the main ring buffer except for
> debugging, in which case you can use trace_printk(), which will cause the
> tracing buffers to be expanded by default.
> 
> Other areas of the kernel should create their own trace array which will be
> created expanded by default too.
> 
> -- Steve


Thanks Steve, that makes sense.

The concrete case I was trying to address is not an upstream in-tree 
user. It is a downstream UEK RDS compatibility path where the legacy 
  
             rds_rt_debug_bitmap module parameter is mapped to RDS 
tracepoints by calling trace_set_clr_event() against the global trace 
array during module init. That can leave the default RDS tracepoints 
recording into the boot-minimum buffer unless userspace expands tracing 
first.

Looking at mainline again, trace-array users are already created 
expanded by default, and the remaining global-buffer use is 
debugging-style. So I agree this generic tracing/events change does not 
have a good upstream justification.

Please drop this patch. We will handle the downstream RDS compatibility 
case downstream, or move it to an explicit userspace/trace-array setup.

Thanks,
Manjunath