On Sun, Jan 31, 2021 at 11:57 AM Matthew Miller
<mattdm(a)fedoraproject.org> wrote:
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?
I'm seeing:
[ 1.179693] Btrfs loaded, crc32c=crc32c-generic, zoned=yes
Someone adventurous might want to figure out how to get it to use
crc32c_intel instead. I think it might need to be compiled into the
kernel.
CONFIG_CRYPTO_CRC32C=y
CONFIG_CRYPTO_CRC32C_INTEL=m
And then retest.
But also, the difference in performance between xxhash and crc32c is
pretty tiny. I'm using all four hashes on various file systems, and up
until there's a heavy IO workload, there's no performance difference
among them.
--
Chris Murphy