[vdo-devel] [dm-devel] [PATCH v2 02/39] Add the MurmurHash3 fast hashing algorithm.

[corwin]

On 5/23/23 6:06 PM, Eric Biggers wrote:
> On Tue, May 23, 2023 at 05:45:02PM -0400, J. corwin Coburn wrote:
>> MurmurHash3 is a fast, non-cryptographic, 128-bit hash. It was originally
>> written by Austin Appleby and placed in the public domain. This version has
>> been modified to produce the same result on both big endian and little
>> endian processors, making it suitable for use in portable persistent data.
>>
>> Signed-off-by: J. corwin Coburn <corwin at redhat.com>
>> ---
>>   drivers/md/dm-vdo/murmurhash3.c | 175 ++++++++++++++++++++++++++++++++
>>   drivers/md/dm-vdo/murmurhash3.h |  15 +++
>>   2 files changed, 190 insertions(+)
>>   create mode 100644 drivers/md/dm-vdo/murmurhash3.c
>>   create mode 100644 drivers/md/dm-vdo/murmurhash3.h
> 
> Do we really need yet another hash algorithm?
> 
> xxHash is another very fast non-cryptographic hash algorithm that is already
> available in the kernel (lib/xxhash.c).
> 
> - Eric

The main reason why vdo uses Murmur3 and not xxHash is that vdo has been 
in deployment since 2013, and, if I am reading correctly, xxHash did not 
have a 128 bit variant until 2019.

It would certainly be possible to switch vdo to xxHash, but it would be 
problematic for existing users.

corwin