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List:       fedora-devel-list
Subject:    Re: Btrfs by default, the compression option
From:       Matthew Miller <mattdm () fedoraproject ! org>
Date:       2020-07-08 19:45:07
Message-ID: 20200708194507.GA28547 () mattdm ! org
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On Wed, Jul 08, 2020 at 11:37:11AM -0600, Chris Murphy wrote:
> If it's the center, I think that favors the mount option approach and
> do it with the lowest level of compression, i.e. zstd:1. But this
> suggests more benchmarking still, to make certain it's well understood
> what the range of write performance hit could be in those scenarios.
> Whereas the curated approach can just bypass most of that question -
> the payload and workload for flatpak and usr and containers is fairly
> fixed across all Fedora users rather than mixed content and workloads
> found in ~/

I just did some quick tests out of curiousity. I tarred up /usr on my
system, resulting in a 9.8GB file. Ran this in my home dir on a
run-of-the-mill Western Digital SSD.


This results in:

    compression     file      compression   % better than 
      level         size         ratio         previous

        1           4.1G        41.36%            - 
        2           3.8G        38.97%           6.1%
        3           3.6G        36.81%           5.9%
        4           3.6G        36.36%           1.2%
        5           3.5G        35.63%           2.8%
        6           3.5G        35.33%           2.0%

        9           3.4G        34.19%            -
       19           2.8G        29.72%            -


That's pretty good even at level 1. I don't think my setup is useful for
timing benchmarks, and also that takes more care than I want to put into it
this minute, but the interesting note is that levels 1-4 are all about the
same in speed (within 10 seconds) and level 5 suddenly 3x slower. I assume
that's not surprising to anyone who knows how zstd works. But also, unless
you go to crazy high levels, the gains above level 3 really drop off.

(19, by the way, is amazingly slow. Took almost an hour.)




-- 
Matthew Miller
<mattdm@fedoraproject.org>
Fedora Project Leader
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