Re: [PATCH bpf-next] bpf: Speed up htab hashing for u32/u64 keys

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

On 9/21/26 6:00 PM, Alexei Starovoitov wrote:
> On Mon Sep 21, 2026 at 3:43 PM UTC, Alexei Starovoitov wrote:
>>>  static inline u32 htab_map_hash(const void *key, u32 key_len, u32 hashrnd)
>>>  {
>>> -	if (likely(key_len % 4 == 0))
>>> +	const u32 *k = key;
>>> +	u32 b;
>>> +
>>> +	if (key_len == sizeof(u32))
>>> +		b = 0;
>>> +	else if (key_len == sizeof(u64))
>>> +		b = k[1];
>>> +	else if (likely(key_len % 4 == 0))
>>>  		return jhash2(key, key_len / 4, hashrnd);
> 
> Nice improvement, but key_size is known at verification time.
> Let's do a step further and specialize htab_map_gen_lookup
> for small key sizes?
> 
Sure, let me try that.