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List:       fedora-devel-list
Subject:    Re: Small rant: installer environment size
From:       "Chris Murphy" <lists () colorremedies ! com>
Date:       2022-12-09 22:08:19
Message-ID: 93c50ede-f2db-4dd9-91d0-8f2084c72c2c () app ! fastmail ! com
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On Fri, Dec 9, 2022, at 7:30 AM, Ray Strode wrote:
> Hi,
> 
> On Thu, Dec 8, 2022 at 2:55 PM Adam Williamson
> <adamwill@fedoraproject.org> wrote:
> > This is the direction Daniel was thinking down. I'm waiting for someone
> > with more expertise to reply, but I suspect the reply is going to be
> > along the lines of "yes, we *can* do that, but it's somewhat tricky
> > work that involves thinking about lots of paths that aren't obvious,
> > and somebody would need to dedicate their time to working on that".
> Presumably we could package the firmware separately and just unpack it
> into place from a udev rule when the hardware is detected?
> 
> But first, do we actually know this is a problem?
> I think you're saying squashfs loads the whole decompressed image into
> memory, but my expectation prior to your mail was that it performs I/O
> on the usb stick (with a cache in between).  If my intuition was right
> and files only hit ram when accessed, then it seems like this is
> pretty much not an issue, right?

From a certain point of view there's a potential inefficiency with squashfs reads in \
that there's a minimum block size that it needs to read in order decompress its 128 \
KiB block. It's possible quite a lot of what's decompressed isn't (immediately) \
needed. But it's still a random access file system. It's not necessary to read the \
whole image into RAM.

Repo metadata is the big hit for netinstall because it's downloaded into /tmp which \
is tmpfs. And DVD already has repomd on it, and only downloads more if you enable \
some other repo. Live doesn't need repomd.

So initially netinstaller uses less memory up until the the Anaconda language \
selection screen appears, at which point it starts background downloading repomd. It \
quickly catches up to, and surpasses, Live media memory consumption.

Off hand, I'm not sure what's producing all the anonymous pages during Live \
installation but it's a fairly linear increase as the installation progresses. Since \
it's an rsync based installation, I'm currently frownie facing pondering the cause of \
the anon page explosion.



-- 
Chris Murphy
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