On Tue, 19 Dec 2023 13:54:17 -0500
Steven Rostedt <rost...@goodmis.org> wrote:
> +/**
> + * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
> + * @buffer: The ring_buffer to set the new page size.
> + * @order: Order of the system pages in one sub buffer page
> + *
> + * By default, one ring buffer pages equals to one system page. This API can
> be
> + * used to set new size of the ring buffer page. The size must be order of
> + * system page size, that's why the input parameter @order is the order of
> + * system pages that are allocated for one ring buffer page:
> + * 0 - 1 system page
> + * 1 - 2 system pages
> + * 3 - 4 system pages
> + * ...
Don't we have the max order of the pages?
> + *
> + * Returns 0 on success or < 0 in case of an error.
> + */
> +int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
> +{
> + int psize;
> +
> + if (!buffer || order < 0)
> + return -EINVAL;
> +
> + if (buffer->subbuf_order == order)
> + return 0;
> +
> + psize = (1 << order) * PAGE_SIZE;
> + if (psize <= BUF_PAGE_HDR_SIZE)
> + return -EINVAL;
> +
> + buffer->subbuf_order = order;
> + buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
> +
> + /* Todo: reset the buffer with the new page size */
> +
I just wonder why there is no reallocate the sub buffers here.
Is it OK to change the sub buffer page size and order while
using the ring buffer?
Thank you,
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
