Re: [U-Boot] [PATCH] Add xxhash hashing support

Dear Dmitry,

In message 1520258115-29823-1-git-send-email-dunaev@tecon.ru you wrote:

From: Dmitry Dunaev dunaev@tecon.ru

---

It would be appropriate to provide an explantion of what you are doing here and why, which advantages it brings, what it costs (in terms of code size), etc.

In short: please provide a proper commit message.

+/*

• • xxHash - Extremely Fast Hash algorithm
• • Copyright (C) 2012-2016, Yann Collet.
• • BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
• • Redistribution and use in source and binary forms, with or without
• • modification, are permitted provided that the following conditions are
• • met:

....

• • This program is free software; you can redistribute it and/or modify it under
• • the terms of the GNU General Public License version 2 as published by the
• • Free Software Foundation. This program is dual-licensed; you may select
• • either version 2 of the GNU General Public License ("GPL") or BSD license
• • ("BSD").

Please use SPDX License Tags and remove the license text.

• • Notice extracted from xxHash homepage:
• • xxHash is an extremely fast Hash algorithm, running at RAM speed limits.
• • It also successfully passes all tests from the SMHasher suite.
• • Comparison (single thread, Windows Seven 32 bits, using SMHasher on a Core 2
• • Duo @3GHz)
• • Name Speed Q.Score Author
• • xxHash 5.4 GB/s 10
• • CrapWow 3.2 GB/s 2 Andrew
• • MumurHash 3a 2.7 GB/s 10 Austin Appleby
• • SpookyHash 2.0 GB/s 10 Bob Jenkins
• • SBox 1.4 GB/s 9 Bret Mulvey
• • Lookup3 1.2 GB/s 9 Bob Jenkins
• • SuperFastHash 1.2 GB/s 1 Paul Hsieh
• • CityHash64 1.05 GB/s 10 Pike & Alakuijala
• • FNV 0.55 GB/s 5 Fowler, Noll, Vo
• • CRC32 0.43 GB/s 9
• • MD5-32 0.33 GB/s 10 Ronald L. Rivest
• • SHA1-32 0.28 GB/s 10
• • Q.Score is a measure of quality of the hash function.
• • It depends on successfully passing SMHasher test set.
• • 10 is a perfect score.
• • A 64-bits version, named xxh64 offers much better speed,
• • but for 64-bits applications only.
• • Name Speed on 64 bits Speed on 32 bits
• • xxh64 13.8 GB/s 1.9 GB/s
• • xxh32 6.8 GB/s 6.0 GB/s

This should probably go to the commit message.

...

• • xxh32_wd() - calculate the 32-bit hash of the input with a given seed.

• •          Triggering the watchdog every 'chunk_sz' bytes of input
    

• •          processed.
    

• • @input: The data to hash.
• • @length: The length of the data to hash.
• • @seed: The seed can be used to alter the result predictably.
• • @chunk_sz: The chunk size for watchdog triggering.
• • Speed on Core 2 Duo @ 3 GHz (single thread, SMHasher benchmark) : 5.4 GB/s

Hm... what is this information good for? How fast is it on a MPC860 at 50 MHz? How fast on a iMX28 at 400 MHz?

• • BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
• • Redistribution and use in source and binary forms, with or without
• • modification, are permitted provided that the following conditions are
• • met:

See above. Clean up all over the place and replace with SPDX tags.

Thanks.

Wolfgang Denk