From 03c4cc385faaa46e5877f499c6b997fef792f8d3 Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Wed, 1 Nov 2017 12:44:45 +0100 Subject: [PATCH] bpf: cpumap micro-optimization in cpu_map_enqueue Discovered that the compiler laid-out asm code in suboptimal way when studying perf report during benchmarking of cpumap. Help the compiler by the marking unlikely code paths. Signed-off-by: Jesper Dangaard Brouer Acked-by: John Fastabend Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/cpumap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c index 86e29cbf7827..ce5b669003b2 100644 --- a/kernel/bpf/cpumap.c +++ b/kernel/bpf/cpumap.c @@ -208,7 +208,7 @@ static struct xdp_pkt *convert_to_xdp_pkt(struct xdp_buff *xdp) headroom = xdp->data - xdp->data_hard_start; metasize = xdp->data - xdp->data_meta; metasize = metasize > 0 ? metasize : 0; - if ((headroom - metasize) < sizeof(*xdp_pkt)) + if (unlikely((headroom - metasize) < sizeof(*xdp_pkt))) return NULL; /* Store info in top of packet */ @@ -656,7 +656,7 @@ int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp, struct xdp_pkt *xdp_pkt; xdp_pkt = convert_to_xdp_pkt(xdp); - if (!xdp_pkt) + if (unlikely(!xdp_pkt)) return -EOVERFLOW; /* Info needed when constructing SKB on remote CPU */ -- 2.11.0