[RFC PATCH 03/24] erofs: add Errno in Rust

[Gao Xiang]

On 2024/9/26 16:10, Ariel Miculas wrote:
> On 24/09/26 09:04, Gao Xiang wrote:
>>


...

> 
> And here [4] you can see the space savings achieved by PuzzleFS. In
> short, if you take 10 versions of Ubuntu Jammy from dockerhub, they take
> up 282 MB. Convert them to PuzzleFS and they only take up 130 MB (this
> is before applying any compression, the space savings are only due to
> the chunking algorithm). If we enable compression (PuzzleFS uses Zstd
> seekable compression), which is a fairer comparison (considering that
> the OCI image uses gzip compression), then we get down to 53 MB for
> storing all 10 Ubuntu Jammy versions using PuzzleFS.
> 
> Here's a summary:
> # Steps
> 
> * I’ve downloaded 10 versions of Jammy from hub.docker.com
> * These images only have one layer which is in tar.gz format
> * I’ve built 10 equivalent puzzlefs images
> * Compute the tarball_total_size by summing the sizes of every Jammy
>    tarball (uncompressed) => 766 MB (use this as baseline)
> * Sum the sizes of every oci/puzzlefs image => total_size
> * Compute the total size as if all the versions were stored in a single
>    oci/puzzlefs repository => total_unified_size
> * Saved space = tarball_total_size - total_unified_size
> 
> # Results
> (See [5] if you prefer the video format)
> 
> | Type | Total size (MB) | Average layer size (MB) | Unified size (MB) | Saved (MB) / 766 MB |
> | --- | --- | --- | --- | --- |
> | Oci (uncompressed) | 766 | 77 | 766 | 0 (0%) |
> | PuzzleFS uncompressed | 748 | 74 | 130 | 635 (83%) |
> | Oci (compressed) | 282 | 28 | 282 | 484 (63%) |
> | PuzzleFS (compressed) | 298 | 30 | 53 | 713 (93%) |
> 
> Here's the script I used to download the Ubuntu Jammy versions and
> generate the PuzzleFS images [6] to get an idea about how I got to these
> results.
> 
> Can we achieve these results with the current erofs features?  I'm
> referring specifically to this comment: "EROFS already supports
> variable-sized chunks + CDC" [7].

Please see
https://erofs.docs.kernel.org/en/latest/comparsion/dedupe.html

	                Total Size (MiB)	Average layer size (MiB)	Saved / 766.1MiB
Compressed OCI (tar.gz)	282.5	28.3	63%
Uncompressed OCI (tar)	766.1	76.6	0%
Uncomprssed EROFS	109.5	11.0	86%
EROFS (DEFLATE,9,32k)	46.4	4.6	94%
EROFS (LZ4HC,12,64k)	54.2	5.4	93%

I don't know which compression algorithm are you using (maybe Zstd?),
but from the result is
   EROFS (LZ4HC,12,64k)  54.2
   PuzzleFS compressed   53?
   EROFS (DEFLATE,9,32k) 46.4

I could reran with EROFS + Zstd, but it should be smaller. This feature
has been supported since Linux 6.1, thanks.

Thanks,
Gao Xiang