From cc555421bc118edd070f41258d6f55f1ccfc2558 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Thu, 31 Aug 2017 23:27:12 -0700 Subject: [PATCH] bpf: Inline LRU map lookup Inline the lru map lookup to save the cost in making calls to bpf_map_lookup_elem() and htab_lru_map_lookup_elem(). Different LRU hash size is tested. The benefit diminishes when the cache miss starts to dominate in the bigger LRU hash. Considering the change is simple, it is still worth to optimize. First column: Size of the LRU hash Second column: Number of lookups/s Before: > for i in $(seq 9 20); do echo "$((2**i+1)): $(./map_perf_test 1024 1 $((2**i+1)) 10000000 | awk '{print $3}')"; done 513: 1132020 1025: 1056826 2049: 1007024 4097: 853298 8193: 742723 16385: 712600 32769: 688142 65537: 677028 131073: 619437 262145: 498770 524289: 316695 1048577: 260038 After: > for i in $(seq 9 20); do echo "$((2**i+1)): $(./map_perf_test 1024 1 $((2**i+1)) 10000000 | awk '{print $3}')"; done 513: 1221851 1025: 1144695 2049: 1049902 4097: 884460 8193: 773731 16385: 729673 32769: 721989 65537: 715530 131073: 671665 262145: 516987 524289: 321125 1048577: 260048 Signed-off-by: Martin KaFai Lau Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/hashtab.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index d246905f2bb1..682f4543fefa 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -514,6 +514,24 @@ static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key) return NULL; } +static u32 htab_lru_map_gen_lookup(struct bpf_map *map, + struct bpf_insn *insn_buf) +{ + struct bpf_insn *insn = insn_buf; + const int ret = BPF_REG_0; + + *insn++ = BPF_EMIT_CALL((u64 (*)(u64, u64, u64, u64, u64))__htab_map_lookup_elem); + *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 2); + *insn++ = BPF_ST_MEM(BPF_B, ret, + offsetof(struct htab_elem, lru_node) + + offsetof(struct bpf_lru_node, ref), + 1); + *insn++ = BPF_ALU64_IMM(BPF_ADD, ret, + offsetof(struct htab_elem, key) + + round_up(map->key_size, 8)); + return insn - insn_buf; +} + /* It is called from the bpf_lru_list when the LRU needs to delete * older elements from the htab. */ @@ -1137,6 +1155,7 @@ const struct bpf_map_ops htab_lru_map_ops = { .map_lookup_elem = htab_lru_map_lookup_elem, .map_update_elem = htab_lru_map_update_elem, .map_delete_elem = htab_lru_map_delete_elem, + .map_gen_lookup = htab_lru_map_gen_lookup, }; /* Called from eBPF program */ -- 2.20.1