kernel 5.4.5
btrfs-progs 5.4
test file is linux.tar (not compressed), it's the only file on the
file system in each case
/dev/sda5 53G 2.8G 50G 6% /mnt none
/dev/sda5 53G 2.2G 50G 5% /mnt zstd 1
/dev/sda5 53G 2.1G 50G 4% /mnt zstd 15
mount and dmesg both show the value for the level I've set; but btrfs
insp dump-t shows extents always have compression 3.
[47567.500812] BTRFS info (device sda5): use zstd compression, level 1
item 14 key (328583 EXTENT_DATA 2060582912) itemoff 15488 itemsize 53
generation 51 type 1 (regular)
extent data disk byte 6461308928 nr 20480
extent data offset 0 nr 131072 ram 131072
extent compression 3 (zstd)
==================
[47793.161246] BTRFS info (device sda5): use zstd compression, level 15 │
item 170 key (328584 EXTENT_DATA 2735341568) itemoff 7220 itemsize 53
generation 54 type 1 (regular)
extent data disk byte 2168475648 nr 24576
extent data offset 0 nr 131072 ram 131072
extent compression 3 (zstd)
I'd expect a bigger difference between level 1 and 15, so I'm a little
suspicious that it really is always using level 3. But it's also
possible that it's just a bug with inspect always reporting level 3.
The rate of the level 15 copy is slower.
--
Chris Murphy
