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([2620:10d:c092:500::7:c6a4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48862793528sm3832853f8f.36.2026.09.22.04.49.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Sep 2026 04:49:31 -0700 (PDT) Message-ID: Date: Tue, 22 Sep 2026 12:49:31 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v2] bpf: Speed up htab lookups for u32/u64 keys To: Alexei Starovoitov , bpf@vger.kernel.org, andrii@kernel.org, daniel@iogearbox.net, kernel-team@meta.com, eddyz87@gmail.com, memxor@gmail.com Cc: Mykyta Yatsenko , Anton Protopopov References: <20260921-hashtab_fast_hashfn-v2-1-79aa962ec56b@meta.com> Content-Language: en-US From: Mykyta Yatsenko In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/22/26 2:40 AM, Alexei Starovoitov wrote: > On Mon, Sep 21, 2026 at 02:28 PM Mykyta Yatsenko wrote: >> + /* >> + * Fold the jhash constant and key length into hashrnd once for the >> + * fixed-size fast paths instead of doing it on every lookup. >> + */ >> + if (htab->map.key_size == sizeof(u32) || >> + htab->map.key_size == sizeof(u64)) >> + htab->hashrnd += JHASH_INITVAL + htab->map.key_size; > > This optimization is probably not needed anymore? > I'll double check with benchmark and remove if not needed in v3.>> -static void *__htab_map_lookup_elem(struct bpf_map *map, void *key) >> +static __always_inline void *__htab_lookup(struct bpf_map *map, void *key, u32 key_size) > > __htab_lookup() is __always_inline, but htab_map_hash() and > lookup_nulls_elem_raw() that consume key_size are not. > Whether memcmp() becomes a single compare in _u32/_u64 variants > is up to the compiler. Make both __always_inline? > Make sense, thanks.