[v5,00/15] ring-buffer/tracing: Allow ring buffer to have bigger sub buffers

Message ID	20231219185414.474197117@goodmis.org (mailing list archive)
Headers	show Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B176D38DFA; Tue, 19 Dec 2023 18:55:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 481CBC433C7; Tue, 19 Dec 2023 18:55:28 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from <rostedt@goodmis.org>) id 1rFfGV-00000003QzN-2fpf; Tue, 19 Dec 2023 13:56:27 -0500 Message-ID: <20231219185414.474197117@goodmis.org> User-Agent: quilt/0.67 Date: Tue, 19 Dec 2023 13:54:14 -0500 From: Steven Rostedt <rostedt@goodmis.org> To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, Andrew Morton <akpm@linux-foundation.org>, Tzvetomir Stoyanov <tz.stoyanov@gmail.com>, Vincent Donnefort <vdonnefort@google.com>, Kent Overstreet <kent.overstreet@gmail.com> Subject: [PATCH v5 00/15] ring-buffer/tracing: Allow ring buffer to have bigger sub buffers Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: <linux-trace-kernel.vger.kernel.org> List-Subscribe: <mailto:linux-trace-kernel+subscribe@vger.kernel.org> List-Unsubscribe: <mailto:linux-trace-kernel+unsubscribe@vger.kernel.org>
Series	ring-buffer/tracing: Allow ring buffer to have bigger sub buffers \| expand [v5,00/15] ring-buffer/tracing: Allow ring buffer to have bigger sub buffers [v5,01/15] ring-buffer: Refactor ring buffer implementation [v5,02/15] ring-buffer: Page size per ring buffer [v5,03/15] ring-buffer: Add interface for configuring trace sub buffer size [v5,04/15] ring-buffer: Set new size of the ring buffer sub page [v5,05/15] ring-buffer: Read and write to ring buffers with custom sub buffer size [v5,06/15] ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure [v5,07/15] ring-buffer: Do no swap cpu buffers if order is different [v5,08/15] ring-buffer: Make sure the spare sub buffer used for reads has same size [v5,09/15] tracing: Update snapshot order along with main buffer order [v5,10/15] tracing: Stop the tracing while changing the ring buffer subbuf size [v5,11/15] ring-buffer: Keep the same size when updating the order [v5,12/15] ring-buffer: Just update the subbuffers when changing their allocation order [v5,13/15] ring-buffer: Add documentation on the buffer_subbuf_order file [v5,14/15] ringbuffer/selftest: Add basic selftest to test changing subbuf order [v5,15/15] tracing: Update subbuffer with kilobytes not page order [v5,16/15] ring-buffer: Use subbuf_order for buffer page masking

Message ID

20231219185414.474197117@goodmis.org (mailing list archive)

Headers

Message-ID: <20231219185414.474197117@goodmis.org>
User-Agent: quilt/0.67
Date: Tue, 19 Dec 2023 13:54:14 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
 linux-trace-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
 Mark Rutland <mark.rutland@arm.com>,
 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Tzvetomir Stoyanov <tz.stoyanov@gmail.com>,
 Vincent Donnefort <vdonnefort@google.com>,
 Kent Overstreet <kent.overstreet@gmail.com>
Subject: [PATCH v5 00/15] ring-buffer/tracing: Allow ring buffer to have
 bigger sub buffers
Precedence: bulk

Series

ring-buffer/tracing: Allow ring buffer to have bigger sub buffers | expand

Message

Steven Rostedt Dec. 19, 2023, 6:54 p.m. UTC

Note, this has been on my todo list since the ring buffer was created back
in 2008.

Tzvetomir last worked on this in 2021 and I need to finally get it in.

His last series was:

  https://lore.kernel.org/linux-trace-devel/20211213094825.61876-1-tz.stoyanov@gmail.com/

With the description of:

   Currently the size of one sub buffer page is global for all buffers and
   it is hard coded to one system page. The patch set introduces configurable
   ring buffer sub page size, per ring buffer. A new user space interface is
   introduced, which allows to change the sub page size of the ftrace buffer,
   per ftrace instance.

I'm pulling in his patches mostly untouched, except that I had to tweak
a few things to forward port them.

The issues I found I added as the last 7 patches to the series, and then
I added documentation and a selftest, and then changed the UI file
from buffer_subbuf_order to buffer_subbuf_size_kb.

Basically, events to the tracing subsystem are limited to just under a
PAGE_SIZE, as the ring buffer is split into "sub buffers" of one page
size, and an event can not be bigger than a sub buffer. This allows users
to change the size of a sub buffer by the order:

  echo 3 > /sys/kernel/tracing/buffer_subbuf_order

[
  last patch updates this to:

  echo 32 > /sys/kernel/tracing/buffer_subbuf_size_kb

]
  

Will make each sub buffer a size of 8 pages (32KB), allowing events to be
almost as big as 8 pages in size (sub buffers do have meta data on them as
well, keeping an event from reaching the same size as a sub buffer).

Changes since v4: https://lore.kernel.org/linux-trace-kernel/20231215175502.106587604@goodmis.org/

- Rebase on latest trace/core

- Fixed a kerneldoc issues reported by kernel test robot


Changes since v3: https://lore.kernel.org/all/20231213181737.791847466@goodmis.org/

- Rebase on trace/core:

  https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git/commit/?h=trace/core&id=59c28cc95f0a9f5556561e2416af4ecf86184b71

Changes since v2: https://lore.kernel.org/all/20231213021914.361709558@goodmis.org/

- Fixed up the subbuf tests to ignore multiple spaces after before the
  'buf' string (same fix as was done for the trace_marker test).

- This time include Cc'ing linux-trace-kernel :-p

Changes since v1: https://lore.kernel.org/all/20231210040448.569462486@goodmis.org/

- Add the last patch that changes the ABI from a file called:

  buffer_subbuf_order  to   buffer_subbuf_size_kb

  That is, I kept the old interface the same, but then added the last
  patch that converts the interface into the one that makes more sense.
  I like keeping this in the git history, especially because of the
  way the implemantion is.

- I rebased on top of trace/core in the:

    git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git

- I made the tests a bit more advanced. Still a smoke test, but it
  now checks if the string written is the same as the string read.