net: page_pool: use alloc_pages_bulk in refill code path

There are cases where the page_pool need to refill with pages from the
page allocator.  Some workloads cause the page_pool to release pages
instead of recycling these pages.

For these workload it can improve performance to bulk alloc pages from the
page-allocator to refill the alloc cache.

For XDP-redirect workload with 100G mlx5 driver (that use page_pool)
redirecting xdp_frame packets into a veth, that does XDP_PASS to create an
SKB from the xdp_frame, which then cannot return the page to the
page_pool.

Performance results under GitHub xdp-project[1]:
 [1] https://github.com/xdp-project/xdp-project/blob/master/areas/mem/page_pool06_alloc_pages_bulk.org

Mel: The patch "net: page_pool: convert to use alloc_pages_bulk_array
variant" was squashed with this patch. From the test page, the array
variant was superior with one of the test results as follows.

	Kernel		XDP stats       CPU     pps           Delta
	Baseline	XDP-RX CPU      total   3,771,046       n/a
	List		XDP-RX CPU      total   3,940,242    +4.49%
	Array		XDP-RX CPU      total   4,249,224   +12.68%

Link: https://lkml.kernel.org/r/20210325114228.27719-10-mgorman@techsingularity.net
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Alexander Lobakin <alobakin@pm.me>
Cc: Alexander Duyck <alexander.duyck@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/net/page_pool.h

@@ -65,7 +65,7 @@
 #define PP_ALLOC_CACHE_REFILL	64
 struct pp_alloc_cache {
 	u32 count;
-	void *cache[PP_ALLOC_CACHE_SIZE];
+	struct page *cache[PP_ALLOC_CACHE_SIZE];
 };
 
 struct page_pool_params {