On Wed, May 29, 2019 at 10:16:59AM +0200, Jesper Dangaard Brouer wrote:
On Thu, 23 May 2019 21:20:35 +0300 Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> wrote:+static struct page *cpsw_alloc_page(struct cpsw_common *cpsw) +{ + struct page_pool *pool = cpsw->rx_page_pool; + struct page *page, *prev_page = NULL; + int try = pool->p.pool_size << 2; + int start_free = 0, ret; + + do { + page = page_pool_dev_alloc_pages(pool); + if (!page) + return NULL; + + /* if netstack has page_pool recycling remove the rest */ + if (page_ref_count(page) == 1) + break; + + /* start free pages in use, shouldn't happen */ + if (prev_page == page || start_free) { + /* dma unmap/puts page if rfcnt != 1 */ + page_pool_recycle_direct(pool, page); + start_free = 1; + continue; + } + + /* if refcnt > 1, page has been holding by netstack, it's pity, + * so put it to the ring to be consumed later when fast cash is + * empty. If ring is full then free page by recycling as above. + */ + ret = ptr_ring_produce(&pool->ring, page);This looks very wrong to me! First of all you are manipulation directly with the internal pool->ring and not using the API, which makes this code un-maintainable.
Yes I know, it's hack, it was with assumption to be dropped once page_pool recycling is added.
Second this is wrong, as page_pool assume the in-variance that pages on the ring have refcnt==1.
Yes, but this is w/o obvious reason, seems like it can work with refcnt > 1 if remove restriction and use >= instead of ==. As I answered on Ilias comment, I'm going to leave version from RFC and drop this one.
+ if (ret) { + page_pool_recycle_direct(pool, page); + continue; + } + + if (!prev_page) + prev_page = page; + } while (try--); + + return page; +}-- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
-- Regards, Ivan Khoronzhuk
