linux-kernel - Re: [PATCH v1] docs: describe how to quickly build Linux

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Date:   Thu, 2 Feb 2023 16:36:59 +0100
From:   Thorsten Leemhuis <linux@...mhuis.info>
To:     Konstantin Ryabitsev <konstantin@...uxfoundation.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonathan Corbet <corbet@....net>,
        Linux regressions mailing list <regressions@...ts.linux.dev>
Subject: Re: [PATCH v1] docs: describe how to quickly build Linux

On 02.02.23 16:08, Konstantin Ryabitsev wrote:
> On Thu, Feb 02, 2023 at 12:15:36PM +0100, Linux kernel regression tracking (Thorsten Leemhuis) wrote:
>> Then I tried creating a shallow clone like this:
>>
>> git clone
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>> --depth 1 -b v6.1
>> git remote set-branches --add origin master
>> git fetch --all --shallow-exclude=v6.1
>> git remote add -t linux-6.1.y linux-stable
>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
>> git fetch --all --shallow-exclude=v6.1
>>
>> This took only roundabout 2 minutes and downloads & stores ~512 MByte
>> data (without checkout).
> 
> Can we also include the option of just downloading the tarball, if it's a
> released version? That's the fastest and most lightweight option 100% of the
> time. :)

Don't worry, that was in there and will stay in there:

+   If you plan to only build one particular kernel version, download
its source
+   archive from https://kernel.org; afterwards extract its content to
'~/linux/'
+   and change into the directory created during extraction.
>> Not totally sure, but the shallow clone somehow feels more appropriate
>> for the use case (reminder, there is a "quickly" in the document title),
>> even if such a clone is less flexible (e.g. users have to manually add
>> stable branches they are interested it; and they need to be careful when
>> using git fetch).
>>
>> That's why I now strongly consider using the shallow clone method by
>> default in v2 of this text. Or does that also create a lot of load on
>> the servers? Or are there other strong reason why using a shallow clone
>> might be a bad idea for this use case?
> 
> As I mentioned elsewhere, this is only a problem when it's done in batch mode
> by CI systems. A full clone uses pregenerated pack files and is very cheap,
> because it's effectively a sendfile operation. A shallow clone requires
> generating a brand new pack, compressing it, and then keeping it around in
> memory for the duration of the clone process. Not a big deal when a few humans
> here and there do it, but when 50 CI nodes do it all at once, it effectively
> becomes a DDoS. :)

Thx again for your insights, much appreciated.

Ciao, Thorsten