From: David Sterba dsterba@suse.com
[ Upstream commit efcfcbc6a36195c42d98e0ee697baba36da94dc8 ]
The implementation of XXHASH is now CPU only but still fast enough to be considered for the synchronous checksumming, like non-generic crc32c.
A userspace benchmark comparing it to various implementations (patched hash-speedtest from btrfs-progs):
Block size: 4096 Iterations: 1000000 Implementation: builtin Units: CPU cycles
NULL-NOP: cycles: 73384294, cycles/i 73 NULL-MEMCPY: cycles: 228033868, cycles/i 228, 61664.320 MiB/s CRC32C-ref: cycles: 24758559416, cycles/i 24758, 567.950 MiB/s CRC32C-NI: cycles: 1194350470, cycles/i 1194, 11773.433 MiB/s CRC32C-ADLERSW: cycles: 6150186216, cycles/i 6150, 2286.372 MiB/s CRC32C-ADLERHW: cycles: 626979180, cycles/i 626, 22427.453 MiB/s CRC32C-PCL: cycles: 466746732, cycles/i 466, 30126.699 MiB/s XXHASH: cycles: 860656400, cycles/i 860, 16338.188 MiB/s
Comparing purely software implementation (ref), current outdated accelerated using crc32q instruction (NI), optimized implementations by M. Adler (https://stackoverflow.com/questions/17645167/implementing-sse-4-2s-crc32c-in...) and the best one that was taken from kernel using the PCLMULQDQ instruction (PCL).
Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/disk-io.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 3c0b3b4ec5ad5..1fb7cb4492bdb 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2328,6 +2328,9 @@ static int btrfs_init_csum_hash(struct btrfs_fs_info *fs_info, u16 csum_type) if (!strstr(crypto_shash_driver_name(csum_shash), "generic")) set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags); break; + case BTRFS_CSUM_TYPE_XXHASH: + set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags); + break; default: break; }