On Wed, 1 Jul 2026 06:38:22 -0400
Steven Rostedt [off-list ref] wrote:

On Wed, 1 Jul 2026 11:04:07 +0100
David Laight [off-list ref] wrote:

quoted

I thought it was just used to do a pid->string lookup when you run 'cat trace'.
But then I found the code that lets userspace read the table....
I guess the latter is used by the userspace code that reads the raw trace buffer.  

Yes, trace-cmd uses it.

...

quoted

The userspace code could probably be given comm[] for all the running
processes and those that exited while tracing_on() set.
(I didn't see anything that would clear the table when the trace buffer
was cleared.)  

Well, that would break trace-cmd. As reading the raw buffers clears the
trace, and trace-cmd reads the saved_cmdlines file *after* it reads the
trace, as during the trace it gets populated.

So you'd need to clear it when tracing is enabled after the buffer is cleared.
Just a matter of getting the timing right.

If trace-cmd is currently given all 6000 entries (if you've run tracing for
long enough), then giving it all the active processes isn't going to be any
more of a problem.
So you could just save comm[] in the process exit path when the trace buffer
is non-empty, or better those started before tracing was last stopped.
You'd need to give trace-cmd the active ones first and delete the entry
from the cache because the pid might have been reused.

All just needs some coding, testing, and fixing of corner cases.

-- David 

-- Steve