From: Jesper Dangaard Brouer <brouer@redhat.com>
Date: Wed, 1 Nov 2017 12:44:45 +0100
Subject: bpf: cpumap micro-optimization in cpu_map_enqueue
Patch-mainline: v4.15-rc1
Git-commit: 03c4cc385faaa46e5877f499c6b997fef792f8d3
References: bsc#1109837
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 <brouer@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
kernel/bpf/cpumap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -208,7 +208,7 @@ static struct xdp_pkt *convert_to_xdp_pk
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_e
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 */