On Tue, 27 Oct 2020 20:04:08 +0100
Lorenzo Bianconi <lore...@kernel.org> wrote:
> +void page_pool_put_page_bulk(struct page_pool *pool, void **data,
> + int count)
> +{
> + struct page *page_ring[XDP_BULK_QUEUE_SIZE];
Maybe we could reuse the 'data' array instead of creating a new array
(2 cache-lines long) for the array of pages?
> + int i, len = 0;
> +
> + for (i = 0; i < count; i++) {
> + struct page *page = virt_to_head_page(data[i]);
> +
> + if (unlikely(page_ref_count(page) != 1 ||
> + !pool_page_reusable(pool, page))) {
> + page_pool_release_page(pool, page);
> + put_page(page);
> + continue;
> + }
> +
> + if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> + page_pool_dma_sync_for_device(pool, page, -1);
Here we sync the entire DMA area (-1), which have a *huge* cost for
mvneta (especially on EspressoBin HW). For this xdp_frame->len is
unfortunately not enough. We will need the *maximum* length touch by
(1) CPU and (2) remote device DMA engine. DMA-TX completion knows the
length for (2). The CPU length (1) is max of original xdp_buff size
and xdp_frame->len, because BPF-helpers could have shrinked the size.
(tricky part is that xdp_frame->len isn't correct in-case of header
adjustments, thus like mvneta_run_xdp we to calc dma_sync size, and
store this in xdp_frame, maybe via param to xdp_do_redirect). Well, not
sure if it is too much work to transfer this info, for this use-case.
> +
> + page_ring[len++] = page;
> + }
> +
> + page_pool_ring_lock(pool);
> + for (i = 0; i < len; i++) {
> + if (__ptr_ring_produce(&pool->ring, page_ring[i]))
> + page_pool_return_page(pool, page_ring[i]);
> + }
> + page_pool_ring_unlock(pool);
> +}
> +EXPORT_SYMBOL(page_pool_put_page_bulk);
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
