On Tue, May 14, 2024 at 1:28 PM Chenliang Li <cliang01.li@xxxxxxxxxxx> wrote:
>
> Introduce helper functions to check whether a buffer can
> be coalesced or not, and gather folio data for later use.
>
> The coalescing optimizes time and space consumption caused
> by mapping and storing multi-hugepage fixed buffers.
>
> A coalescable multi-hugepage buffer should fully cover its folios
> (except potentially the first and last one), and these folios should
> have the same size. These requirements are for easier later process,
Nit: for easier processing later
> also we need same size'd chunks in io_import_fixed for fast iov_iter
> adjust.
>
> Signed-off-by: Chenliang Li <cliang01.li@xxxxxxxxxxx>
> ---
> io_uring/rsrc.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++
> io_uring/rsrc.h | 10 +++++++
> 2 files changed, 88 insertions(+)
>
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index 65417c9553b1..d08224c0c5b0 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -871,6 +871,84 @@ static int io_buffer_account_pin(struct io_ring_ctx *ctx, struct page **pages,
> return ret;
> }
>
> +static bool __io_sqe_buffer_try_coalesce(struct page **pages, int nr_pages,
> + struct io_imu_folio_data *data)
> +{
> + struct folio *folio = page_folio(pages[0]);
> + unsigned int count = 1;
> + int i;
> +
> + data->nr_pages_mid = folio_nr_pages(folio);
> + if (data->nr_pages_mid == 1)
> + return false;
> +
> + data->folio_shift = folio_shift(folio);
> + data->folio_size = folio_size(folio);
> + data->nr_folios = 1;
> + /*
> + * Check if pages are contiguous inside a folio, and all folios have
> + * the same page count except for the head and tail.
> + */
> + for (i = 1; i < nr_pages; i++) {
> + if (page_folio(pages[i]) == folio &&
> + pages[i] == pages[i-1] + 1) {
> + count++;
> + continue;
> + }
> +
> + if (data->nr_folios == 1)
> + data->nr_pages_head = count;
> + else if (count != data->nr_pages_mid)
> + return false;
> +
> + folio = page_folio(pages[i]);
> + if (folio_size(folio) != data->folio_size)
> + return false;
> +
> + count = 1;
> + data->nr_folios++;
> + }
> + if (data->nr_folios == 1)
> + data->nr_pages_head = count;
> +
> + return true;
> +}
> +
> +static bool io_sqe_buffer_try_coalesce(struct page **pages, int nr_pages,
> + struct io_imu_folio_data *data)
> +{
> + int i, j;
> +
> + if (nr_pages <= 1 ||
> + !__io_sqe_buffer_try_coalesce(pages, nr_pages, data))
> + return false;
> +
> + /*
> + * The pages are bound to the folio, it doesn't
> + * actually unpin them but drops all but one reference,
> + * which is usually put down by io_buffer_unmap().
> + * Note, needs a better helper.
> + */
> + if (data->nr_pages_head > 1)
> + unpin_user_pages(&pages[1], data->nr_pages_head - 1);
> +
> + j = data->nr_pages_head;
> + nr_pages -= data->nr_pages_head;
> + for (i = 1; i < data->nr_folios; i++) {
> + unsigned int nr_unpin;
> +
> + nr_unpin = min_t(unsigned int, nr_pages - 1,
> + data->nr_pages_mid - 1);
> + if (nr_unpin == 0)
> + break;
> + unpin_user_pages(&pages[j+1], nr_unpin);
> + j += data->nr_pages_mid;
> + nr_pages -= data->nr_pages_mid;
> + }
> +
> + return true;
> +}
> +
> static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
> struct io_mapped_ubuf **pimu,
> struct page **last_hpage)
> diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
> index c032ca3436ca..b2a9d66b76dd 100644
> --- a/io_uring/rsrc.h
> +++ b/io_uring/rsrc.h
> @@ -50,6 +50,16 @@ struct io_mapped_ubuf {
> struct bio_vec bvec[] __counted_by(nr_bvecs);
> };
>
> +struct io_imu_folio_data {
> + /* Head folio can be partially included in the fixed buf */
> + unsigned int nr_pages_head;
> + /* For non-head/tail folios, has to be fully included */
> + unsigned int nr_pages_mid;
> + unsigned int nr_folios;
> + unsigned int folio_shift;
> + size_t folio_size;
> +};
> +
> void io_rsrc_node_ref_zero(struct io_rsrc_node *node);
> void io_rsrc_node_destroy(struct io_ring_ctx *ctx, struct io_rsrc_node *ref_node);
> struct io_rsrc_node *io_rsrc_node_alloc(struct io_ring_ctx *ctx);
> --
> 2.34.1
>
>
Looks good:
Reviewed-by: Anuj Gupta <anuj20.g@xxxxxxxxxxx>
--
Anuj Gupta
