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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 <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>
This commit is contained in:
Jesper Dangaard Brouer 2017-11-01 12:44:45 +01:00 committed by David S. Miller
parent 14e83bf829
commit 03c4cc385f
1 changed files with 2 additions and 2 deletions
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4
kernel/bpf/cpumap.c
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@ -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 */