On Fri, Apr 19, 2019 at 11:31:56AM +0300, Ilias Apalodimas wrote:
Hi Ivan,
+static struct page *cpsw_alloc_page(struct cpsw_common *cpsw)
+{
+ struct page_pool *pool = cpsw->rx_page_pool;
+ struct page *page;
+ int i = 0;
+
+ do {
+ page = page_pool_dev_alloc_pages(pool);
+ if (!page)
+ return NULL;
+
+ /* skip pages used by skb netstack */
I think the comment here is wrong and might confuse people.
The page ref cnt is 1, which means the packet was *processed* and netstack is
done with it, hence you can re-use it.
If it's !=1 then you correctly unmap the buffer and decrease the ref cnt, so it
will eventually be freed and not returned to the pool, right?
It's compensation substitution for page_pool support in skb netsack.
And should be considered in combine with:
skb = build_skb(xmeta, cpsw_rxbuf_total_len(pkt_size));
...
page_pool_recycle_direct(pool, page);
page_ref_inc(page);
netif_receive_skb(skb);
Here order is important.
I will correct comments in final version (w/o overloading) ofc, leaving
thinking environment for people. I think it's fair enough about this.
+ if (page_ref_count(page) == 1)
+ break;
+
+ /* it's a pitty, but free page */
+ page_pool_recycle_direct(pool, page);
+ } while (++i < descs_pool_size);
+
+ return page;
+}
+
/Ilias
--
Regards,
Ivan Khoronzhuk
