quoted
Any regression in page pool can be avoided in the common case that
does not use device mem by placing that behind a static_branch. Would
that address your performance concerns?
No. This will not help.
The problem is that every where in the page_pool code it is getting
polluted with:
if (page_is_page_pool_iov(page))
call-some-iov-func-instead()
Like: the very central piece of getting the refcnt:
+static inline int page_pool_page_ref_count(struct page *page)
+{
+ if (page_is_page_pool_iov(page))
+ return page_pool_iov_refcount(page_to_page_pool_iov(page));
+
+ return page_ref_count(page);
+}
The fast-path of the PP is used for XDP_DROP scenarios, and is currently
around 14 cycles (tsc). Thus, any extra code in this code patch will
change the fast-path.
With static_branch disabled, it would only insert a NOP?