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Generic kernels, CFLAGS and processor families? [SOLVED]
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dufeu
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PostPosted: Thu Aug 16, 2018 6:59 pm    Post subject: Generic kernels, CFLAGS and processor families? [SOLVED] Reply with quote

I've been tasked with setting up a number of the Windows based PCs on our network as 'dual (gentoo lunix) boot'.

To support this, I'm setting up two VM clients to serve as package builders and binary package servers. There be one of each for 32 bit and 64 bit systems.

The target PCs represent mostly a variety of Intel based systems. I've read the Gento Wiki Safe_CFLAGS article, the QEMU '-cpu' help and a number of forum posts discussing CFLAG choices.

The 64 bit targets will be loaded with KDE Plasma and Google Chrome as the desktop and browser provided. i.e. CPUID = "sse2" is required.

The 32 bit targets will be loaded with LXQT and Firefox as the desktop and browser provided.

Each will also be provisioned with 'LibreOffice'.

As I read the available documentation and forum posts, for the 64 bit VM client, I want to invoke QEMU with:
Code:
qemu-system-x86_64 -cpu qemu64 ...
and on the VM client I want to set:
/etc/portage/make.conf:
CFLAGS="-mtune=generic -O2 -pipe"
while the kernel should be configured:
Code:
Processor Type and features
   Processor family: 'generic-x86_64'

I'm trying to avoid retaining the 32bit PCs. If I can't, then I want to invoke QEMU with:
Code:
qemu-system-x86_64 -cpu qemu32 ...
and on the VM client I want to set:
/etc/portage/make.conf:
CFLAGS="-mtune=generic -O2 -pipe"
while the kernel should be configured:
Code:
Processor Type and features
   Processor family: 'pentium-pro'

One of the things I haven't been able to determine is whether qemu64/kvm4 provide 'sse2' or not. If this isn't true, then which '-cpu' option would be best (most generic with 'sse2' support) to use?
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Last edited by dufeu on Fri Aug 17, 2018 11:19 am; edited 1 time in total
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NeddySeagoon
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PostPosted: Thu Aug 16, 2018 7:08 pm    Post subject: Reply with quote

dufeu,

You should use -march=i686 in the 32 bit make.conf.
The Pentium Pro was the first i686 CPU.

Can you still build firefox and libreoffice in a 32 bit address space?
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Maitreya
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PostPosted: Thu Aug 16, 2018 7:51 pm    Post subject: Reply with quote

What is the percentage of 32bit machines you are asked to support?
Asking this, because 32bit is a lot of maintenance to do "on the side'.
To my experience sometimes having to sell "no" works better in the long run.
One arch is already the challenge enough I guess, especially if the other one is a dying breed.
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dufeu
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PostPosted: Thu Aug 16, 2018 7:57 pm    Post subject: Reply with quote

NeddySeagoon wrote:
You should use -march=i686 in the 32 bit make.conf.
The Pentium Pro was the first i686 CPU.
Good point. Will do so.
Quote:
Can you still build firefox and libreoffice in a 32 bit address space?

I did Firefox as recently as about 14 months ago. LibreOffice is still officially providing 32bit binaries and source code packages even for their latest 6.1.0 stable. So ... probably. If I can't, then as good an excuse as any to finally get rid of them. ;)

In terms of packages, the only thing I've had a problem compiling recently has actually been 'dev-qt/qtengine-5.11.1' and the most recent 'dev-qt/qtwebkit'. I've been testing/building a new 64bit Gentoo based VM client and ran into memory problems with both packages. This is _after_ successfully building 'gcc-7.3.0'. I had to invoke QEMU with -m 2560M to get qtengine to build. See bug#660356 and bug#663770.

Surprised the heck out of me.
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dufeu
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PostPosted: Thu Aug 16, 2018 8:19 pm    Post subject: Reply with quote

Maitreya wrote:
What is the percentage of 32bit machines you are asked to support?
Asking this, because 32bit is a lot of maintenance to do "on the side'.
To my experience sometimes having to sell "no" works better in the long run.
One arch is already the challenge enough I guess, especially if the other one is a dying breed.

There's only a handful but this is Florida. The keyword here is 'cheap' in terms of cash outlays. How long it takes labor time never seems to matter.

Having said that, I'd be delighted to dump them. Really. If I come across a reasonable 'deal breaker', I'm going to take it.

It's not just the lack of capability, it's also their high runtime cost too.

However, the boss is building on my previous volunteer sideline (when I used to live in NJ) of re-purposing retired PCs for use in non-profits and for retired people. I had set up a few binary Gentoo package servers so it was pretty easy to recondition the old PCs and send them out. He's looking for more of the same. It's one of those things where I'll have to let him experience some of the pain personally before he believes it. ;)
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josephg
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PostPosted: Fri Aug 17, 2018 7:18 am    Post subject: Reply with quote

NeddySeagoon wrote:
Can you still build firefox and libreoffice in a 32 bit address space?

I still 32bit on all computers, as i didn't want mixups. Much easier. All working very well with firefox and libreoffice too.
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dufeu
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PostPosted: Fri Aug 17, 2018 11:43 am    Post subject: Reply with quote

josephg wrote:
I still 32bit on all computers, as i didn't want mixups. Much easier. All working very well with firefox and libreoffice too.
Life in 32bit land is fine but has several restrictions that must be accepted. Within those restrictions, 32bit is indeed completely fine and I have no problems with it either. The restrictions are:
  • No gaming
  • No Google Chrome
  • No 1080p movie playback

You can upgrade your GPU to alleviate some of this but most of the available old equipment simply isn't up to it without spending money. None of the 32bit PCs with built-in graphics can handle anything beyond 720p video playback. You can do some tricks with transcoding but ... The biggest problem with video playback is the memory bandwidth requirements simply can't be met. You must transcode and reduce the memory stream the system bus needs to deal with.

There are certainly plenty of uses for 32bit equipment, the only real question is whether the restrictions on those uses work for it's intended user. Several of our 32bit desktops are dual 1080p monitors. Can't watch HD video but SD video is fine.

Like any other PC, you just have to match up it's capabilities with the intended user.
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