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Re: When substitute download + decompression is CPU-bound
From: |
Guillaume Le Vaillant |
Subject: |
Re: When substitute download + decompression is CPU-bound |
Date: |
Fri, 29 Jan 2021 12:23:52 +0100 |
User-agent: |
mu4e 1.4.14; emacs 27.1 |
Pierre Neidhardt <mail@ambrevar.xyz> skribis:
> Hi Ludo!
>
> Ludovic Courtès <ludo@gnu.org> writes:
>
>> I suppose a possible agenda would be:
>>
>> 1. Start providing zstd susbstitutes anytime. However, most clients
>> will keep choosing lzip because it usually compresses better.
>>
>> 2. After the next release, stop providing lzip substitutes and provide
>> only gzip + zstd-19.
>>
>> This option has the advantage that it wouldn’t break any installation.
>
> But why would we keep gzip since it offers no benefits compared to zstd?
> It feels like continuing to carry a (huge) burden forever...
>
> Besides, dropping Lzip seems like a step backward in my opinion. Users
> with lower bandwidth (or simply further away from Berlin) will be
> impacted a lot.
>
> I would opt for dropping gzip instead, only to keep zstd-19 and lzip-9
> (possibly plzip-9 if we update the bindings).
>
>> It’s not as nice as the ability to choose a download strategy, as we
>> discussed earlier, but implementing that download strategy sounds
>> tricky.
>
> If the user can choose their favourite substitute compression, I believe
> it's usually enough since they are the best judge of their bandwidth /
> hardware requirements.
>
> Wouldn't this simple enough?
Here are a few numbers for the installation time in seconds (download
time + decompression time) when fetching 580 MB of substitutes for
download speeds between 0.5 MB/s and 20 MB/s.
| Download speed | gzip -9 | lzip -9 | zstd -19 |
|----------------+---------+---------+----------|
| 0.5 | 287 | 151 | 181 |
| 1.0 | 144 | 78 | 91 |
| 1.5 | 97 | 54 | 61 |
| 2.0 | 73 | 42 | 46 |
| 2.5 | 59 | 35 | 37 |
| 3.0 | 49 | 30 | 31 |
| 3.5 | 42 | 27 | 26 |
| 4.0 | 37 | 24 | 23 |
| 4.5 | 33 | 22 | 21 |
| 5.0 | 30 | 21 | 19 |
| 5.5 | 28 | 19 | 17 |
| 6.0 | 25 | 18 | 16 |
| 6.5 | 24 | 17 | 14 |
| 7.0 | 22 | 17 | 14 |
| 7.5 | 21 | 16 | 13 |
| 8.0 | 20 | 15 | 12 |
| 8.5 | 18 | 15 | 11 |
| 9.0 | 18 | 14 | 11 |
| 9.5 | 17 | 14 | 10 |
| 10.0 | 16 | 13 | 10 |
| 11.0 | 15 | 13 | 9 |
| 12.0 | 14 | 12 | 8 |
| 13.0 | 13 | 12 | 8 |
| 14.0 | 12 | 11 | 7 |
| 15.0 | 11 | 11 | 7 |
| 16.0 | 11 | 11 | 6 |
| 17.0 | 10 | 10 | 6 |
| 18.0 | 10 | 10 | 6 |
| 19.0 | 9 | 10 | 5 |
| 20.0 | 9 | 10 | 5 |
When the download speed is lower than 3.5 MB/s, Lzip is better, and
above that speed Zstd is better.
As Gzip is never the best choice, it would make sense to drop it, even
if we have to wait a little until everyone has updated their Guix daemon
to a version with at least Lzip support.
I think there are many people (like me) with a download speed slower
than 3 MB/s, so like Pierre I would prefer keeping "lzip -9" and
"zstd -19".
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- Re: When substitute download + decompression is CPU-bound, Guillaume Le Vaillant, 2021/01/07
- Re: When substitute download + decompression is CPU-bound, Pierre Neidhardt, 2021/01/07
- Re: When substitute download + decompression is CPU-bound, Ludovic Courtès, 2021/01/14
- Re: When substitute download + decompression is CPU-bound, Nicolò Balzarotti, 2021/01/14
- Re: When substitute download + decompression is CPU-bound, Pierre Neidhardt, 2021/01/15
- Re: When substitute download + decompression is CPU-bound, Ludovic Courtès, 2021/01/28
- Re: When substitute download + decompression is CPU-bound, Pierre Neidhardt, 2021/01/29
- Re: When substitute download + decompression is CPU-bound,
Guillaume Le Vaillant <=
- Re: When substitute download + decompression is CPU-bound, Nicolò Balzarotti, 2021/01/29
- Re: When substitute download + decompression is CPU-bound, Pierre Neidhardt, 2021/01/29
- Re: When substitute download + decompression is CPU-bound, Guillaume Le Vaillant, 2021/01/29
- Re: When substitute download + decompression is CPU-bound, Nicolò Balzarotti, 2021/01/29
- Re: When substitute download + decompression is CPU-bound, zimoun, 2021/01/29