linux-kernel - Re: [PATCH] trace: Correct comments about list of pages in buffer

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Message-ID: <20170216093349.387d1b9c@gandalf.local.home>
Date:   Thu, 16 Feb 2017 09:33:49 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joel Fernandes <joelaf@...gle.com>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] trace: Correct comments about list of pages in buffer

On Thu, 16 Feb 2017 02:17:28 -0800
Joel Fernandes <joelaf@...gle.com> wrote:

> Comments related to list of pages in the ring buffer seem to be incorrect.
> This patch corrects them.
> 
> Signed-off-by: Joel Fernandes <joelaf@...gle.com>
> ---
>  kernel/trace/trace.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index d7449783987a..94d508c08c7e 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -262,11 +262,11 @@ unsigned long long ns2usecs(u64 nsec)
>  /*
>   * The global_trace is the descriptor that holds the tracing
>   * buffers for the live tracing. For each CPU, it contains
> - * a link list of pages that will store trace entries. The
> - * page descriptor of the pages in the memory is used to hold
> - * the link list by linking the lru item in the page descriptor
> - * to each of the pages in the buffer per CPU.

Wow, that's a description of the very first (and poor) implementation
of the ring buffer.

> - *
> + * a link list of pages that will store trace entries.
> + * Each page is wrapped by a buffer_page descriptor which contains
> + * a list element used to hold the list of pages by linking with
> + * other list elements of other buffer_page descriptors (for each
> + * of the pages) in the ring buffer per CPU.

Actually, this comment doesn't even belong here anymore. The code lives
elsewhere.

Want to send another patch that just nukes this?

Thanks!

-- Steve

>   * For each active CPU there is a data field that holds the
>   * pages for the buffer for that CPU. Each CPU has the same number
>   * of pages allocated for its buffer.