Re: [PATCH v7 02/13] user_events: Add minimal support for trace_event into ftrace

Steven Rostedt
2021-12-10T17:43:11Z

On Fri, 10 Dec 2021 19:43:58 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> > +/* Limit how long of an event name plus args within the subsystem. */
> > +#define MAX_EVENT_DESC 512
> > +#define EVENT_NAME(user_event) ((user_event)->tracepoint.name)
> > +#define MAX_FIELD_ARRAY_SIZE (2 * PAGE_SIZE)
>
> I don't recommend to record the event which size is more than a page size...
> Maybe 256 entries?
> It is also better to limit the total size of the event and the number
> of fields (arguments).
>
> Steve, can we write such a big event data on the trace buffer?

In the future yes!

https://lore.kernel.org/all/20211125175253.186422-1-tz.stoyanov@gmail.com/

But it will still require some configuration changes from user space. But
that said, if the user wants to add a larger size, then they can do so (in
the future).

-- Steve