On Tue, 17 Oct 2023 13:41:18 -0700 Alexander Duyck wrote: > I am thinking of this from a software engineering perspective. This > symmetric-xor aka simplified-toeplitz is actually much cheaper to > implement in software than the original. As such I would want it to be > considered a separate algorithm as I could make use of something like > that when having to implement RSS in QEMU for instance. That's exactly why XOR and CRC32 _algorithms_ already exist. CPUs have instructions to do them word at a time. ETH_RSS_HASH_TOP_BIT, /* Configurable RSS hash function - Toeplitz */ ETH_RSS_HASH_XOR_BIT, /* Configurable RSS hash function - Xor */ ETH_RSS_HASH_CRC32_BIT, /* Configurable RSS hash function - Crc32 */ If efficient SW implementation is important why do some weird bastardized para-toeplitz and not crc32? Hashes fairly well from what I recall with the older NFPs. x86 has an instruction for it, IIRC it was part of SSE but on normal registers. > Based on earlier comments it doesn't change the inputs, it just > changes how I have to handle the data and the key. It starts reducing > things down to something like the Intel implementation of Flow > Director in terms of how the key gets generated and hashed. About Flow Director I know only that it is bad :)
