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 <bro...@redhat.com>
---
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 */
