dmesg snippet (on Intel E3815 CPU):
[ 0.499794] efivars: duplicate variable: Events-...
[ 0.560048] raid6: sse2x1 gen() 932 MB/s
[ 0.616732] raid6: sse2x1 xor() 1488 MB/s
[ 0.673362] raid6: sse2x2 gen() 1665 MB/s
[ 0.730014] raid6: sse2x2 xor() 1777 MB/s
[ 0.786688] raid6: sse2x4 gen() 2635 MB/s
[ 0.843352] raid6: sse2x4 xor() 1732 MB/s
[ 0.843355] raid6: using algorithm sse2x4 gen() 2635 MB/s
[ 0.843356] raid6: .... xor() 1732 MB/s, rmw enabled
[ 0.843358] raid6: using ssse3x2 recovery algorithm
[ 0.846998] xor: measuring software checksum speed
[ 0.880025] prefetch64-sse: 4605.600 MB/sec
[ 0.913372] generic_sse: 4176.000 MB/sec
[ 0.913375] xor: using function: prefetch64-sse (4605.600 MB/sec)
[ 0.952233] Btrfs loaded, crc32c=crc32c-intel
[ 0.957669] SCSI subsystem initialized
# lsmod | grep btrfs
btrfs 1323008 3
xor 24576 1 btrfs
zstd_decompress 94208 1 btrfs
zstd_compress 188416 1 btrfs
raid6_pq 122880 1 btrfs
# modinfo btrfs | grep 'filename:\|depends:'
filename: /lib/modules/4.14.8-1-ARCH/kernel/fs/btrfs/btrfs.ko.xz
depends: zstd_compress,zstd_decompress,raid6_pq,xor
---
This system doesn't use raid5 neither raid6 nor any RAID at all.
The wish is that btrfs can be loaded at run-time with/without loading
kernel modules raid6_pq neither xor.
Saving:
1. ± 0.4 seconds of boot time (10% of boot until root)
2. ± 150k of RAM
3. ± 75k of disk space
For other cases, I can imagine a root system that doesn't need btrfs
raid, and user data volumes that do use raid6_pq. In such delay cases it
is welcome that btrfs-noraid can be loaded first, and the raid modules
and benchmarking during/after init.
New kernel command-line parameters?
a.) disable, like:
- btrfs=noraid6_pq
- btrfs=noraid (=no xor at all)
b.) delay raid6_pq and xor module loading, for cases where root mount
doesn't need raid6_pq and/or xor.
A new entry at https://btrfs.wiki.kernel.org/index.php/Project_ideas is
welcome.
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
