[PATCH bpf-next v1 1/2] xdp: recycle Page Pool backed skbs built from XDP frames

From: Alexander Lobakin <aleksander.lobakin@intel.com>
To: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>
Cc: "Alexander Lobakin" <aleksander.lobakin@intel.com>,
	"Maciej Fijalkowski" <maciej.fijalkowski@intel.com>,
	"Larysa Zaremba" <larysa.zaremba@intel.com>,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"Song Liu" <song@kernel.org>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"Jakub Kicinski" <kuba@kernel.org>,
	bpf@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH bpf-next v1 1/2] xdp: recycle Page Pool backed skbs built from XDP frames
Date: Wed,  1 Mar 2023 17:03:14 +0100	[thread overview]
Message-ID: <20230301160315.1022488-2-aleksander.lobakin@intel.com> (raw)
In-Reply-To: <20230301160315.1022488-1-aleksander.lobakin@intel.com>

__xdp_build_skb_from_frame() state(d):

/* Until page_pool get SKB return path, release DMA here */

Page Pool got skb pages recycling in April 2021, but missed this
function.

xdp_release_frame() is relevant only for Page Pool backed frames and it
detaches the page from the corresponding Pool in order to make it
freeable via page_frag_free(). It can instead just mark the output skb
as eligible for recycling if the frame is backed by a PP. No change for
other memory model types (the same condition check as before).
cpumap redirect and veth on Page Pool drivers now become zero-alloc (or
almost).

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 net/core/xdp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/xdp.c b/net/core/xdp.c
index 8c92fc553317..a2237cfca8e9 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -658,8 +658,8 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 	 * - RX ring dev queue index	(skb_record_rx_queue)
 	 */
 
-	/* Until page_pool get SKB return path, release DMA here */
-	xdp_release_frame(xdpf);
+	if (xdpf->mem.type == MEM_TYPE_PAGE_POOL)
+		skb_mark_for_recycle(skb);
 
 	/* Allow SKB to reuse area used by xdp_frame */
 	xdp_scrub_frame(xdpf);
-- 
2.39.2

