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Mon, 21 Sep 2026 10:00:31 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 21 Sep 2026 17:00:30 +0000 Message-Id: Cc: "Mykyta Yatsenko" Subject: Re: [PATCH bpf-next] bpf: Speed up htab hashing for u32/u64 keys From: "Alexei Starovoitov" To: "Mykyta Yatsenko" , , , , , , X-Mailer: aerc 0.17.0 References: <20260921-hashtab_fast_hashfn-v1-1-f92ae72cefcd@meta.com> <179000542526.3934731.994864591824564797@gmail.com> In-Reply-To: <179000542526.3934731.994864591824564797@gmail.com> 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 hash= rnd) > > { > > - if (likely(key_len % 4 =3D=3D 0)) > > + const u32 *k =3D key; > > + u32 b; > > + > > + if (key_len =3D=3D sizeof(u32)) > > + b =3D 0; > > + else if (key_len =3D=3D sizeof(u64)) > > + b =3D k[1]; > > + else if (likely(key_len % 4 =3D=3D 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?