netdev - [PATCH bpf v3 3/5] libbpf: remove likely/unlikely in xsk.h

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Date:   Tue, 16 Apr 2019 14:58:10 +0200
From:   Magnus Karlsson <magnus.karlsson@...el.com>
To:     magnus.karlsson@...el.com, bjorn.topel@...el.com, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org
Cc:     bpf@...r.kernel.org, bruce.richardson@...el.com,
        ciara.loftus@...el.com, ilias.apalodimas@...aro.org,
        xiaolong.ye@...el.com, ferruh.yigit@...el.com,
        qi.z.zhang@...el.com, georgmueller@....net
Subject: [PATCH bpf v3 3/5] libbpf: remove likely/unlikely in xsk.h

This patch removes the use of likely and unlikely in xsk.h since they
create a dependency on Linux headers as reported by several
users. There have also been reports that the use of these decreases
performance as the compiler puts the code on two different cache lines
instead of on a single one. All in all, I think we are better off
without them.

Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")
Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
---
 tools/lib/bpf/xsk.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
index 1b35c40..f264f24 100644
--- a/tools/lib/bpf/xsk.h
+++ b/tools/lib/bpf/xsk.h
@@ -109,7 +109,7 @@ static inline __u32 xsk_cons_nb_avail(struct xsk_ring_cons *r, __u32 nb)
 static inline size_t xsk_ring_prod__reserve(struct xsk_ring_prod *prod,
 					    size_t nb, __u32 *idx)
 {
-	if (unlikely(xsk_prod_nb_free(prod, nb) < nb))
+	if (xsk_prod_nb_free(prod, nb) < nb)
 		return 0;
 
 	*idx = prod->cached_prod;
@@ -133,7 +133,7 @@ static inline size_t xsk_ring_cons__peek(struct xsk_ring_cons *cons,
 {
 	size_t entries = xsk_cons_nb_avail(cons, nb);
 
-	if (likely(entries > 0)) {
+	if (entries > 0) {
 		/* Make sure we do not speculatively read the data before
 		 * we have received the packet buffers from the ring.
 		 */
-- 
2.7.4