From: Björn Töpel <bjorn.topel@xxxxxxxxx>
In commit 43e74c0267a3 ("bpf_xdp_redirect_map: Perform map lookup in
eBPF helper") the bpf_redirect_map() helper learned to do map lookup,
which means that the explicit lookup in the XDP program for AF_XDP is
not needed.
This commit removes the map lookup, which simplifies the BPF code and
improves the performance for the "rx_drop" [1] scenario with ~4%.
[1] # xdpsock -i eth0 -z -r
Suggested-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
Signed-off-by: Björn Töpel <bjorn.topel@xxxxxxxxx>
---
tools/lib/bpf/xsk.c | 24 +++++-------------------
1 file changed, 5 insertions(+), 19 deletions(-)
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index b0f532544c91..8e35de3cb443 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -278,29 +278,15 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
*
* // A set entry here means that the correspnding queue_id
* // has an active AF_XDP socket bound to it.
- * if (bpf_map_lookup_elem(&xsks_map, &index))
- * return bpf_redirect_map(&xsks_map, index, 0);
- *
- * return XDP_PASS;
+ * return bpf_redirect_map(&xsks_map, index, XDP_PASS);
* }
*/
struct bpf_insn prog[] = {
- /* r1 = *(u32 *)(r1 + 16) */
- BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_1, 16),
- /* *(u32 *)(r10 - 4) = r1 */
- BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_1, -4),
- BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
- BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
- BPF_LD_MAP_FD(BPF_REG_1, xsk->xsks_map_fd),
- BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
- BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
- BPF_MOV32_IMM(BPF_REG_0, 2),
- /* if r1 == 0 goto +5 */
- BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 5),
- /* r2 = *(u32 *)(r10 - 4) */
+ /* r2 = *(u32 *)(r1 + 16) */
+ BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 16),
BPF_LD_MAP_FD(BPF_REG_1, xsk->xsks_map_fd),
- BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_10, -4),
- BPF_MOV32_IMM(BPF_REG_3, 0),
+ /* r3 = XDP_PASS */
+ BPF_MOV32_IMM(BPF_REG_3, 2),
BPF_EMIT_CALL(BPF_FUNC_redirect_map),
/* The jumps are to this instruction */
BPF_EXIT_INSN(),
--
2.20.1
