linux-kernel - Re: [PATCH] tracing: Have large events show up as '[LINE TOO BIG]' instead of nothing

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Date:   Sun, 10 Dec 2023 10:34:15 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] tracing: Have large events show up as '[LINE TOO BIG]'
 instead of nothing

On Sun, 10 Dec 2023 09:11:40 -0500
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> On 2023-12-09 17:10, Steven Rostedt wrote:
> [...]
> >              <...>-852     [001] .....   121.550551: tracing_mark_write[LINE TOO BIG]
> >              <...>-852     [001] .....   121.550581: tracing_mark_write: 78901234  
> 
> Failing to print an entire message because it does not fit in the
> buffer size is rather inconvenient.

Yes I agree, and luckily it hasn't been called out as an issue. Note, I hit
this because I extended the trace_marker buffer before increasing the
trace_seq size. Otherwise, the trace_marker just breaks it up. This can now
only be triggered by internal changes.

> 
> It would be better to print the partial line, and end the line with
> a <TRUNCATED LINE> tag.

Agreed, but I don't have time to do that (I already spent way too much time
on this than I had allocated). I decided to just do what the trace_pipe
currently does, and leave "print partial line" to another day when I can
allocate time on this.

Hmm, this could be added to the "TODO" list that was talked about in
ksummit-discuss.

-- Steve