From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Mark Rutland <mark.rutland@arm.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: Re: [PATCH 13/14] ring-buffer: Add documentation on the buffer_subbuf_order file
Date: Sun, 10 Dec 2023 09:28:55 -0500 [thread overview]
Message-ID: <298be08b-b010-47e8-b6d5-78910b63a6a7@efficios.com> (raw)
In-Reply-To: <20231210040451.982725347@goodmis.org>
On 2023-12-09 22:54, Steven Rostedt wrote:
[...]
> + buffer_subbuf_order:
> +
> + This sets or displays the sub buffer page size order. The ring buffer
> + is broken up into several same size "sub buffers". An event can not be
> + bigger than the size of the sub buffer. Normally, the sub buffer is
> + the size of the architecture's page (4K on x86). The sub buffer also
> + contains meta data at the start which also limits the size of an event.
> + That means when the sub buffer is a page size, no event can be larger
> + than the page size minus the sub buffer meta data.
The fact that the user ABI documentation for this tracer parameter needs
to dig into details about architecture page size is a good indicator
that this ABI is not at the abstraction level it should be (pages vs
bytes).
Thanks,
Mathieu
> +
> + The buffer_subbuf_order allows the user to change the size of the sub
> + buffer. As the sub buffer is a set of pages by the power of 2, thus
> + the sub buffer total size is defined by the order:
> +
> + order size
> + ---- ----
> + 0 PAGE_SIZE
> + 1 PAGE_SIZE * 2
> + 2 PAGE_SIZE * 4
> + 3 PAGE_SIZE * 8
> +
> + Changing the order will change the sub buffer size allowing for events
> + to be larger than the page size.
> +
> + Note: When changing the order, tracing is stopped and any data in the
> + ring buffer and the snapshot buffer will be discarded.
> +
> free_buffer:
>
> If a process is performing tracing, and the ring buffer should be
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
next prev parent reply other threads:[~2023-12-10 14:29 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-10 3:54 [PATCH 00/14] ring-buffer/tracing: Allow ring buffer to have bigger sub buffers Steven Rostedt
2023-12-10 3:54 ` [PATCH 01/14] ring-buffer: Refactor ring buffer implementation Steven Rostedt
2023-12-10 3:54 ` [PATCH 02/14] ring-buffer: Page size per ring buffer Steven Rostedt
2023-12-10 3:54 ` [PATCH 03/14] ring-buffer: Add interface for configuring trace sub buffer size Steven Rostedt
2023-12-10 3:54 ` [PATCH 04/14] ring-buffer: Set new size of the ring buffer sub page Steven Rostedt
2023-12-10 3:54 ` [PATCH 05/14] ring-buffer: Read and write to ring buffers with custom sub buffer size Steven Rostedt
2023-12-10 3:54 ` [PATCH 06/14] ring-buffer: Clear pages on error in ring_buffer_subbuf_order_set() failure Steven Rostedt
2023-12-10 3:54 ` [PATCH 07/14] ring-buffer: Do no swap cpu buffers if order is different Steven Rostedt
2023-12-10 3:54 ` [PATCH 08/14] ring-buffer: Make sure the spare sub buffer used for reads has same size Steven Rostedt
2023-12-10 3:54 ` [PATCH 09/14] tracing: Update snapshot order along with main buffer order Steven Rostedt
2023-12-10 3:54 ` [PATCH 10/14] tracing: Stop the tracing while changing the ring buffer subbuf size Steven Rostedt
2023-12-10 3:54 ` [PATCH 11/14] ring-buffer: Keep the same size when updating the order Steven Rostedt
2023-12-10 3:54 ` [PATCH 12/14] ring-buffer: Just update the subbuffers when changing their allocation order Steven Rostedt
2023-12-10 3:54 ` [PATCH 13/14] ring-buffer: Add documentation on the buffer_subbuf_order file Steven Rostedt
2023-12-10 14:28 ` Mathieu Desnoyers [this message]
2023-12-10 3:54 ` [PATCH 14/14] ringbuffer/selftest: Add basic selftest to test chaning subbuf order Steven Rostedt
2023-12-10 14:26 ` Mathieu Desnoyers
2023-12-10 15:44 ` Steven Rostedt
2023-12-10 14:17 ` [PATCH 00/14] ring-buffer/tracing: Allow ring buffer to have bigger sub buffers Mathieu Desnoyers
2023-12-10 15:38 ` Steven Rostedt
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