linux-kernel - Re: [PATCH] trace_seq: Increase the buffer size to almost two pages

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Message-ID: <20231211132837.24488ec1@gandalf.local.home>
Date:   Mon, 11 Dec 2023 13:28:37 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] trace_seq: Increase the buffer size to almost two pages

On Mon, 11 Dec 2023 21:46:27 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> > 
> > By increasing the trace_seq buffer to almost two pages, it can now print
> > out the first line.
> > 
> > This also subtracts the rest of the trace_seq fields from the buffer, so
> > that the entire trace_seq is now PAGE_SIZE aligned.  
> 
> Ok, but I just a bit concern about the memory consumption.
> Since this is very specific case, can we make it configurable later?

I was concerned about this too, but it looks like it's allocated and later
freed in every location except for a couple of instances.

One is "tracepoint_print_iter" which is used to pipe tracepoints to printk.
I think we can possibly make that allocated too.

The other is in ftrace_dump, which I don't think we can easily allocate
that. Although, we could have it allocated at boot up if
ftrace_dump_on_oops() is enabled.

Another KTODO?

> 
> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 

Thanks!

-- Steve