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SubjectRe: [PATCH v2 1/2] ring-buffer: Introducing ring-buffer mapping functions
On Wed, 22 Mar 2023 10:22:43 +0000
Vincent Donnefort <vdonnefort@google.com> wrote:

> +#include <linux/types.h>
> +
> +struct ring_buffer_meta_page_header {
> +#if __BITS_PER_LONG == 64
> + __u64 entries;
> + __u64 overrun;
> +#else
> + __u32 entries;
> + __u32 overrun;
> +#endif
> + __u32 pages_touched;
> + __u32 meta_page_size;
> + __u32 reader_page; /* page ID for the reader page */
> + __u32 nr_data_pages; /* doesn't take into account the reader_page */
> + __u32 data_page_head; /* ring-buffer head as an offset from data_start */
> + __u32 data_start; /* offset within the meta page */
> +};
> +

I've been playing with this a bit, and I'm thinking, do we need the
data_pages[] array on the meta page?

I noticed that I'm not even using it.

Currently, we need to do a ioctl every time we finish with the reader page,
and that updates the reader_page in the meta data to point to the next page
to read. When do we need to look at the data_start section?

-- Steve

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