Re: nvme+btrfs+compression sensibility and benchmark

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On 18.04.2018 22:24, Chris Murphy wrote:
> On Wed, Apr 18, 2018 at 10:38 AM, Austin S. Hemmelgarn <ahferroin7@xxxxxxxxx
>> wrote:
> 
>> For reference, the zstd compression in BTRFS uses level 3 by default (as
>> does zlib compression IIRC), though I'm not sure about lzop (I think it
>> uses the lowest compression setting).
>>
> 
> 
> The user space tool, zstd, does default to 3, according to its man page.
> 
>        -#     # compression level [1-19] (default: 3)
> 
> 
> However, the kernel is claiming it's level 0, which doesn't exist in the
> man page. So I have no idea what we're using. This is what I get with mount
> option compress=zstd
> 

Currently the kernel-mode zstd compression doesn't really support any
levels (compress_level is not set, even if it's passed, and even then
zstd_set_level is also unimplemented). So this number doesn't really
make any difference.

> [    4.097858] BTRFS info (device nvme0n1p9): use zstd compression, level 0
> 
> 
> 
> --
> Chris Murphy
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