Originally posted by Danny3
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Updated Zstd Implementation Merged For Linux 6.2
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Originally posted by Danny3 View Post
LOL!
Somebody has good observation skills!
But when you have only 119 GiB of storage and not a high-end CPU, your only hope is BTRFS + Zstd compression, but that must not slow down everything down, especially when extracting / compressing files or copy / move folders with lots of things inside.
And if you can install and play a few games that would be great!
But to be able to do all that, considering the storage and CPU limitations, at least you better have the latest and the greatest improvements in BTRFS and Zstd.
BTRFS keep getting them, but Zstd did not.
Now with Linux 6.2 I'm very happy that they both have.
Too bad that 6.1 is the LTS one as 6.2 seems to be really wonderful and the one that makes pretty much everyone happy!
That is not 100% accurate since it does not do padding like ZFS and btrfs do to round up to say the nearest 4KB sector, but it should still do a good job of showing the difference between the two in terms of space savings.Last edited by ryao; 20 December 2022, 01:53 AM.
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Originally posted by ryao View Post
I wonder if in-tree filesystems will have problems because of this, since zstd’s constants was changed in 1.5.0 such that the output from the compressor is not the same as it was in older versions. At least in ZFS, it is assumed that compress(decompress(old_compress(data))) = old_compress(data). This makes updating zstd potentially problematic without treating it as a different version of the compressor internally, which is something that ZFS implemented alongside zstd support so that future updates could be done.
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Originally posted by piorunz View PostDoes Btrfs benefit from this also? Meaning filesystem compression uses that updated Zstd, or it has its own zstd built-in into Btrfs code?Last edited by cynic; 20 December 2022, 07:47 AM.
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Originally posted by ryao View Post
I use ZFS with zstd and a 1M recordsize on my machine for that. I get higher compression than btrfs can provide even with zstd since btrfs is limited to compressing in 64KB blocks at a time, which harms the compression ratio. You can test this by manually using zstd to compress the Linux kernel at different block sizes. You should see zstd compresses it much more efficiently with a 1MB block size than a 64KB block size.
That is not 100% accurate since it does not do padding like ZFS and btrfs do to round up to say the nearest 4KB sector, but it should still do a good job of showing the difference between the two in terms of space savings.
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I feel for all these people excited about using Zstd Zram so they can literally download more ram. Seriously, I feel bad for those folks. The way I figure, if you have so little ram that Zstd's ~2.5x compression ratio actually matters when compared to LZ4's ~1.5x compression ratio so you're compelled to limit your ram speed to an SSD or slower must be a sucky position to be in; especially if it's a system that can't be upgraded. IMHO, once you have 16GB or more ram, Zram for swap is a "just in case some shit needs swap precaution" than something that's actually necessary. That's why I use a 4GB LZ4 Zram with my 32GB of memory. I care about throughput over space savings so all I need is some compression that enhances throughput and not a compressor that will slow throughput for enhanced compression. Zstd is great, but it isn't designed for high performance IO....just the O. The I is rather limited using the non-fast values.
Zswap...I mixed feelings about using Zstd there since it uses ram and a backing drive and the backing drive is likely slower than ram. In that case we might as well throttle the compressor to the lowest common denominator storage's write speed which will probably be Zstd 1 or 2 using in-kernel options and assuming an SSD and a preference towards more throughput.Last edited by skeevy420; 20 December 2022, 10:21 AM.
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Originally posted by skeevy420 View PostI feel for all these people excited about using Zstd Zram so they can literally download more ram. Seriously, I feel bad for those folks. The way I figure, if you have so little ram that Zstd's ~2.5x compression ratio actually matters when compared to LZ4's ~1.5x compression ratio so you're compelled to limit your ram speed to an SSD or slower must be a sucky position to be in; especially if it's a system that can't be upgraded. IMHO, once you have 16GB or more ram, Zram for swap is a "just in case some shit needs swap precaution" than something that's actually necessary. That's why I use a 4GB LZ4 Zram with my 32GB of memory. I care about throughput over space savings so all I need is some compression that enhances throughput and not a compressor that will slow throughput for enhanced compression. Zstd is great, but it isn't designed for high performance IO....just the O. The I is rather limited using the non-fast values.
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Originally posted by Danny3 View Post
But when you have only 119 GiB of storage and not a high-end CPU, your only hope is BTRFS + Zstd compression, but that must not slow down everything down, especially when extracting / compressing files or copy / move folders with lots of things inside.
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Originally posted by Weasel View PostThat's just you. More RAM is always good, even if it's "slower".
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