Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 21 Dec 2023 09:11:01 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH v5 04/15] ring-buffer: Set new size of the ring buffer sub page |
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On Wed, 20 Dec 2023 11:56:02 -0500 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Thu, 21 Dec 2023 01:34:56 +0900 > Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: > > > On Tue, 19 Dec 2023 13:54:18 -0500 > > Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > From: "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> > > > > > > There are two approaches when changing the size of the ring buffer > > > sub page: > > > 1. Destroying all pages and allocating new pages with the new size. > > > 2. Allocating new pages, copying the content of the old pages before > > > destroying them. > > > The first approach is easier, it is selected in the proposed > > > implementation. Changing the ring buffer sub page size is supposed to > > > not happen frequently. Usually, that size should be set only once, > > > when the buffer is not in use yet and is supposed to be empty. > > > > > > Link: https://lore.kernel.org/linux-trace-devel/20211213094825.61876-5-tz.stoyanov@gmail.com > > > > > > > OK, this actually reallocate the sub buffers when a new order is set. > > BTW, with this change, if we set a new order, the total buffer size will be > > changed too? Or reserve the total size? I think either is OK but it should > > be described in the document. (e.g. if it is changed, user should set the > > order first and set the total size later.) > > > > Patch 11 keeps the same size of the buffer. As I would think that would be > what the user would expect. And not only that, it breaks the latency > tracers if it doesn't keep the same size.
Got it!
Thanks!
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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