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09-06-2010 05:27 PM

Gentoo 32bit->64bit: How?
 
Hi,

My box is a working and fully configured Gentoo system, which is
uptodate.

For the sake of being able to address more RAM and for more
calculation power (mainly for rendering purposes) I want to
migrate to 64bit.

I googled for some tutorial but found nothing appropiate (one post
asked for the downtime to be expected while migrating a server --
something which not applies to me...).

My questions are:
1) Is there a performance gain, when migrating to 64bit if the
target applications supports 64bit?
2) Is it possible - if( true ){ how(); } - to """simply"""
"convert" a 32bit system to 64 bit.
"Simply" in my case means: Simpler ways than starting right
from the bare metal of a virgin harddisk and doing the same
stuff I did for the current system again... ;)
3) Is there some tutorial, which show me the path to go?

Thank you very much in advance for any help!

Best regards,
mcc

Florian Philipp 09-06-2010 06:22 PM

Gentoo 32bit->64bit: How?
 
Am 06.09.2010 19:27, schrieb meino.cramer@gmx.de:
> Hi,
>
> My box is a working and fully configured Gentoo system, which is
> uptodate.
>
> For the sake of being able to address more RAM and for more
> calculation power (mainly for rendering purposes) I want to
> migrate to 64bit.
>
> I googled for some tutorial but found nothing appropiate (one post
> asked for the downtime to be expected while migrating a server --
> something which not applies to me...).
>
> My questions are:
> 1) Is there a performance gain, when migrating to 64bit if the
> target applications supports 64bit?
> 2) Is it possible - if( true ){ how(); } - to """simply"""
> "convert" a 32bit system to 64 bit.
> "Simply" in my case means: Simpler ways than starting right
> from the bare metal of a virgin harddisk and doing the same
> stuff I did for the current system again... ;)
> 3) Is there some tutorial, which show me the path to go?
>

Concerning the performance gain:
Yes, there is. Besides all the improvements when dealing with data types
larger than 32bit you also gain a more general improvement:
More general usage registers on your CPU. That means less stress on
cache and RAM because more operands can be kept ready to usage. It also
speeds up function calls in general because a limited number of
parameters do not need to be passed by storing them on-stack but by
storing them in registers.

Converting:
Look at the mailing list archives. This question had been asked a number
of times over the last few years.

Hope this helps
Florian Philipp

Norman Rieß 09-06-2010 06:44 PM

Gentoo 32bit->64bit: How?
 
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Hash: SHA1

Am 06.09.2010 19:27, schrieb meino.cramer@gmx.de:
> Hi,
>
> My questions are:
> 1) Is there a performance gain, when migrating to 64bit if the
> target applications supports 64bit?
> 2) Is it possible - if( true ){ how(); } - to """simply"""
> "convert" a 32bit system to 64 bit.
> "Simply" in my case means: Simpler ways than starting right
> from the bare metal of a virgin harddisk and doing the same
> stuff I did for the current system again... ;)
> 3) Is there some tutorial, which show me the path to go?
>
> Thank you very much in advance for any help!
>
> Best regards,
> mcc
>

The only way i know to migrate to 64bit is a reinstallation. But the
config files are the same of cause, so it should not be so hard as the
first install if you save your /etc and /home.

The CPU vendors tell, that 64bit code is faster on their 64bit capable
CPUs. Personally i newer thought, "oh yes i feel it, this is 64bit". If
there is a speed gain, it is marginal or only in special cases.

So if you only want to switch to 64bit because of the memory, you could
also use PAE till you want to reinstall anyway.
Nevertheless 64bit on a 64bit capable CPU seems like the way to go :-).

Regards,
Norman

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"Jason Carson" 09-06-2010 07:43 PM

Gentoo 32bit->64bit: How?
 
Check out this, it should answer most of your questions...

http://www.gentoo.org/doc/en/gentoo-amd64-faq.xml#perfup

> Hi,
>
> My box is a working and fully configured Gentoo system, which is
> uptodate.
>
> For the sake of being able to address more RAM and for more
> calculation power (mainly for rendering purposes) I want to
> migrate to 64bit.
>
> I googled for some tutorial but found nothing appropiate (one post
> asked for the downtime to be expected while migrating a server --
> something which not applies to me...).
>
> My questions are:
> 1) Is there a performance gain, when migrating to 64bit if the
> target applications supports 64bit?
> 2) Is it possible - if( true ){ how(); } - to """simply"""
> "convert" a 32bit system to 64 bit.
> "Simply" in my case means: Simpler ways than starting right
> from the bare metal of a virgin harddisk and doing the same
> stuff I did for the current system again... ;)
> 3) Is there some tutorial, which show me the path to go?
>
> Thank you very much in advance for any help!
>
> Best regards,
> mcc
>
>
>
>
>
>

Mark Knecht 09-06-2010 07:58 PM

Gentoo 32bit->64bit: How?
 
On Mon, Sep 6, 2010 at 10:27 AM, <meino.cramer@gmx.de> wrote:
> Hi,
>
> My box is a working and fully configured Gentoo system, which is
> uptodate.
>
> For the sake of being able to address more RAM and for more
> calculation power (mainly for rendering purposes) I want to
> migrate to 64bit.
>
> I googled for some tutorial but found nothing appropiate (one post
> asked for the downtime to be expected while migrating a server --
> something which not applies to me...).
>
> My questions are:
> 1) Is there a performance gain, when migrating to 64bit if the
> * target applications supports 64bit?
> 2) Is it possible - if( true ){ *how(); } - to """simply"""
> * "convert" a 32bit system to 64 bit.
> * "Simply" in my case means: Simpler ways than starting right
> * from the bare metal of a virgin harddisk and doing the same
> * stuff I did for the current system again... ;)
> 3) Is there some tutorial, which show me the path to go?
>
> Thank you very much in advance for any help!
>
> Best regards,
> mcc
>

I think there are some performance advantages but frankly I don't
'feel' them running my systems. None the less if my system is 64-bit
capable I build 64-bit.

There is no 'conversion' or 'upgrade' path that I know about. The way
I did what you are talking about is to build a second Gentoo install
of 64-bit on the same system. and then reference my same home
directories which are on a partition by themselves. Make sure you use
the same ID numbers for users and groups, etc., but if you do that you
can still run 32-bit until the 64-bit is running and stable, and then
wipe the 32-bit partitions to get the disk space back.

I used the 32-bit grub installation, added the 64-bit kernel, and then
never installed grub from within 64-bit. The old version is still out
there and still boots even though the 32-bit install no longer
exists.

Hope this helps,
Mark


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