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List:       fedora-devel-list
Subject:    btrfs hash algorithm (should xxhash be the default?)
From:       Matthew Miller <mattdm () fedoraproject ! org>
Date:       2021-01-31 18:57:04
Message-ID: 20210131185704.GA18831 () mattdm ! org
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On my Intel i7 laptop, xxhash is a small but clear performance win over
crc32c:

    $ ./hash-speedtest  10000000
    Block size:     4096
    Iterations:     10000000
    Implementation: builtin

        NULL-NOP: cycles:   1372543560, c/i      137
     NULL-MEMCPY: cycles:   2844174884, c/i      284
          CRC32C: cycles:   9673117404, c/i      967
          XXHASH: cycles:   7129819594, c/i      712
          SHA256: cycles: 649914613520, c/i    64991
         BLAKE2b: cycles: 153513008046, c/i    15351


And I'm given to understand that this is even more the case on newer CPUs.

Plus, it's 64 bit instead of 32 bit. The 256-bit algorithms are obviously
much, much slower and probably not right for a default, but should we
consider making xxhash the default for Fedora Linux systems with btrfs?

-- 
Matthew Miller
<mattdm@fedoraproject.org>
Fedora Project Leader
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