On 24/09/26 06:46, Gao Xiang wrote: > > > On 2024/9/26 17:51, Ariel Miculas wrote: > > On 24/09/26 04:25, Gao Xiang wrote: > > > > > > > > > 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 > > > > Great, I see you've used the same example as I did. Though I must admit > > I'm a little surprised there's no mention of PuzzleFS in your document. > > Why I need to mention and even try PuzzleFS here (there are too many > attempts why I need to try them all)? It just compares to the EROFS > prior work. > > > > > > > > > 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. > > > > The average layer size is very impressive for EROFS, great work. > > However, if we multiply the average layer size by 10, we get the total > > size (5.4 MiB * 10 ~ 54.2 MiB), whereas for PuzzleFS, we see that while > > the average layer size is 30 MIB (for the compressed case), the unified > > size is only 53 MiB. So this tells me there's blob sharing between the > > different versions of Ubuntu Jammy with PuzzleFS, but there's no sharing > > with EROFS (what I'm talking about is deduplication across the multiple > > versions of Ubuntu Jammy and not within one single version). > > Don't make me wrong, I don't think you got the point. > > First, what you asked was `I'm referring specifically to this > comment: "EROFS already supports variable-sized chunks + CDC"`, > so I clearly answered with the result of compressed data global > deduplication with CDC. > > Here both EROFS and Squashfs compresses 10 Ubuntu images into > one image for fair comparsion to show the benefit of CDC, so It might be a fair comparison, but that's not how container images are distributed. You're trying to argue that I should just use EROFS and I'm showing you that EROFS doesn't currently support the functionality provided by PuzzleFS: the deduplication across multiple images. > I believe they basically equal to your `Unified size`s, so > the result is > > Your unified size > EROFS (LZ4HC,12,64k) 54.2 > PuzzleFS compressed 53? > EROFS (DEFLATE,9,32k) 46.4 > > That is why I used your 53 unified size to show EROFS is much > smaller than PuzzleFS. > > The reason why EROFS and SquashFS doesn't have the `Total Size`s > is just because we cannot store every individual chunk into some > seperate file. Well storing individual chunks into separate files is the entire point of PuzzleFS. > > Currently, I have seen no reason to open arbitary kernel files > (maybe hundreds due to large folio feature at once) in the page > fault context. If I modified `mkfs.erofs` tool, I could give > some similar numbers, but I don't want to waste time now due > to `open arbitary kernel files in the page fault context`. > > As I said, if PuzzleFS finally upstream some work to open kernel > files in page fault context, I will definitely work out the same > feature for EROFS soon, but currently I don't do that just > because it's very controversal and no in-tree kernel filesystem > does that. The PuzzleFS kernel filesystem driver is still in an early POC stage, so there's still a lot more work to be done. Regards, Ariel > > Thanks, > Gao Xiang
