ZRAM Will See Greater Performance On Linux 5.1 - It Changed Its Default Compressor

[phoronix]

Phoronix: ZRAM Will See Greater Performance On Linux 5.1 - It Changed Its Default Compressor

For those relying upon ZRAM to provide a compressed block device in RAM for cases like using it for SWAP or /tmp, with Linux 5.1 you might find it performing better than earlier kernels...

http://www.phoronix.com/scan.php?page=news_item&px=ZRAM-Linux-5.1-Better-Perform

[mercutio]

seems odd that they don't just use lz4

[sdack]

seems odd that they don't just use lz4

It's a series of patches to improve the LZO compressor on ARM CPUs. It's not about which algorithm to choose. You still can choose lz4 over lzo (and lzo-rle) I'd imagine.

[latalante]

seems odd that they don't just use lz4

Who forbids you to use it?
You have a choice: lzo, lzo-rle, lz4, zstd, zlib.

Before you decide, do some real testing.
I will tell you in real battle lzo beats the rest of the headlamp.

[JensRex]

I will tell you in real battle lzo beats the rest of the headlamp.

By what metric?

[mcloud]

Wish one could use zram for more things than just swap, pretty-much like windows 10

[Weasel]

Who forbids you to use it?
You have a choice: lzo, lzo-rle, lz4, zstd, zlib.

Before you decide, do some real testing.
I will tell you in real battle lzo beats the rest of the headlamp.

It beats zstd?

[andreano]

A checklist for vendors of vendor specific kernels for memory constrained little ARM boards:

* Actually include the zram kernel module.

TechNexion doesn't.

[reavertm]

Ah, good old RLE. You have been forgotten my old friend. Surprising it wasn't part of lzo already given it's so trivial to implement and adds almost zero CPU and memory cost.
Should be indeed beneficial for ramdisks or swap partitions where large blobs can be zero-initialised.

[andreano]

Does it beat zstd?

In other words, can zstd beat lzo and lz4 in their own domain, namely speed:

Compressor	Ratio	Compression	Decompression
zstd-1.3.4-1	2.877	470 MB/s	1380 MB/s
brotli 1.0.2 -0	2.701	410 MB/s	430 MB/s
quicklz 1.5.0 -1	2.238	550 MB/s	710 MB/s
lzo1x 2.09 -1	2.108	650 MB/s	830 MB/s
lz4 1.8.1	2.101	750 MB/s	3700 MB/s
snappy 1.1.4	2.091	530 MB/s	1800 MB/s
lzf 3.6 -1	2.077	400 MB/s	860 MB/s

(taken from https://github.com/facebook/zstd)

I'm amazed to see that zstd in its fastest setting almost keeps up with these special-purpose fast compressors, and actually manages to beat regular lzo in decompression! We don't have the numbers for lzo-rle, and it's hard to extrapolate 30% from regular lzo, since we don't know how much comes from compression and decompression, but assuming it's a pure decompression speedup (since that's what you get by making the algorithm more complex), that would be upwards of 60%, and a close race between lzo-rle and zstd on the decompression side. However, nothing that would dethrone lz4 as the bilateral speed king. Of course, the result will depend a bit on your test data.