As per disscussion in Page Pool bulk allocator thread [0], there are two functions in Page Pool core code that are marked as 'noinline'. The reason for this is not so clear, and even if it was made to reduce hotpath overhead, in fact it only makes things worse. As both of these functions as being called only once through the code, they could be inlined/folded into the non-static entry point. However, 'noinline' marks effectively prevent from doing that and induce totally unneeded fragmentation (baseline -> after removal):
add/remove: 0/3 grow/shrink: 1/0 up/down: 1024/-1096 (-72) Function old new delta page_pool_alloc_pages 100 1124 +1024 page_pool_dma_map 164 - -164 page_pool_refill_alloc_cache 332 - -332 __page_pool_alloc_pages_slow 600 - -600 (taken from Mel's branch, hence factored-out page_pool_dma_map()) 1124 is a normal hotpath frame size, but these jumps between tiny page_pool_alloc_pages(), page_pool_refill_alloc_cache() and __page_pool_alloc_pages_slow() are really redundant and harmful for performance. This simple removal of 'noinline' keywords bumps the throughput on XDP_PASS + napi_build_skb() + napi_gro_receive() on 25+ Mbps for 1G embedded NIC. [0] https://lore.kernel.org/netdev/20210317222506.1266004-1-aloba...@pm.me Signed-off-by: Alexander Lobakin <aloba...@pm.me> --- net/core/page_pool.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/net/core/page_pool.c b/net/core/page_pool.c index ad8b0707af04..589e4df6ef2b 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -102,7 +102,6 @@ EXPORT_SYMBOL(page_pool_create); static void page_pool_return_page(struct page_pool *pool, struct page *page); -noinline static struct page *page_pool_refill_alloc_cache(struct page_pool *pool) { struct ptr_ring *r = &pool->ring; @@ -181,7 +180,6 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool, } /* slow path */ -noinline static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool, gfp_t _gfp) { -- 2.31.0
