If the value size in a bloom filter is a multiple of 4, then the jhash2()
function is used to compute hashes. The length parameter of this function
equals to the number of 32-bit words in input. Compute it in the hot path
instead of pre-computing it, as this is translated to one extra shift to
divide the length by four vs. one extra memory load of a pre-computed length.
Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
---
kernel/bpf/bloom_filter.c | 17 ++---------------
1 file changed, 2 insertions(+), 15 deletions(-)
diff --git a/kernel/bpf/bloom_filter.c b/kernel/bpf/bloom_filter.c
index db19784601a7..540331b610a9 100644
--- a/kernel/bpf/bloom_filter.c
+++ b/kernel/bpf/bloom_filter.c
@@ -16,13 +16,6 @@ struct bpf_bloom_filter {
struct bpf_map map;
u32 bitset_mask;
u32 hash_seed;
- /* If the size of the values in the bloom filter is u32 aligned,
- * then it is more performant to use jhash2 as the underlying hash
- * function, else we use jhash. This tracks the number of u32s
- * in an u32-aligned value size. If the value size is not u32 aligned,
- * this will be 0.
- */
- u32 aligned_u32_count;
u32 nr_hash_funcs;
unsigned long bitset[];
};
@@ -32,9 +25,8 @@ static u32 hash(struct bpf_bloom_filter *bloom, void *value,
{
u32 h;
- if (bloom->aligned_u32_count)
- h = jhash2(value, bloom->aligned_u32_count,
- bloom->hash_seed + index);
+ if (likely(value_size % 4 == 0))
+ h = jhash2(value, value_size / 4, bloom->hash_seed + index);
else
h = jhash(value, value_size, bloom->hash_seed + index);
@@ -152,11 +144,6 @@ static struct bpf_map *bloom_map_alloc(union bpf_attr *attr)
bloom->nr_hash_funcs = nr_hash_funcs;
bloom->bitset_mask = bitset_mask;
- /* Check whether the value size is u32-aligned */
- if ((attr->value_size & (sizeof(u32) - 1)) == 0)
- bloom->aligned_u32_count =
- attr->value_size / sizeof(u32);
-
if (!(attr->map_flags & BPF_F_ZERO_SEED))
bloom->hash_seed = get_random_u32();
--
2.34.1
