dump tree always shows compression level 3, zstd

dump tree always shows compression level 3, zstd

[Chris Murphy]

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

Re: dump tree always shows compression level 3, zstd

[Qu Wenruo]

[-- Attachment #1.1: Type: text/plain, Size: 1889 bytes --]



On 2019/12/21 下午2:27, Chris Murphy wrote:
> 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)

This number is not compression level, but compression algorithm.

typedef enum {
        BTRFS_COMPRESS_NONE  = 0,
        BTRFS_COMPRESS_ZLIB  = 1,
        BTRFS_COMPRESS_LZO   = 2,
        BTRFS_COMPRESS_ZSTD  = 3,
        BTRFS_COMPRESS_TYPES = 3,
        BTRFS_COMPRESS_LAST  = 4,
} btrfs_compression_type;

Level is not recorded in that field.

Thanks,
Qu

> 
> 
> ==================
> 
> [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.
> 


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: dump tree always shows compression level 3, zstd

[Chris Murphy]

On Fri, Dec 20, 2019 at 11:34 PM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>
>
>
> On 2019/12/21 下午2:27, Chris Murphy wrote:
> > 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)
>
> This number is not compression level, but compression algorithm.
>
> typedef enum {
>         BTRFS_COMPRESS_NONE  = 0,
>         BTRFS_COMPRESS_ZLIB  = 1,
>         BTRFS_COMPRESS_LZO   = 2,
>         BTRFS_COMPRESS_ZSTD  = 3,
>         BTRFS_COMPRESS_TYPES = 3,
>         BTRFS_COMPRESS_LAST  = 4,
> } btrfs_compression_type;
>
> Level is not recorded in that field.

Oh lovely, that's embarrassing. Thanks for the answer!


-- 
Chris Murphy