Re: [gentoo-user] 32to64 bit migration guide

[Alan McKinnon]

Apparently, though unproven, at 21:08 on Tuesday 07 September 2010, SpaceCake 
did opine thusly:

> Thank you.
>
> The reason to change to 64bit is maybe I'll have 8 GB instead of 4GB of
> memory. PAE is already enabled in kernel, so I have no problem accessing
> memory above 3Gbyte. Is there any performance increase can be expected if I
> spend my time on this migration/reinstall?

Are you doing massively parallel floating point computations that would 
benefit from a full 64 bit data structure?

If yes, then you will see a performance increase. The amount is, well, YMMV.
If no, then you won't.

What you will get is not being limited by that 3G per process limit and the 
overhead of PAE.

I have 100+ servers at work. There are only a few that require 64 bit - 4 huge 
database servers and oddly enough the RT ticket queue box. It's the queue for 
abuse@<where_i_work> so it gets hammered pretty heavily. But we install 64 bit 
OSes everywhere for consistency sake.

It is a fallacy (fairly common unfortunately) that 64 bit gives a performance 
increase per se. It does not. RAM speed, disk speed, network speed, bus speed 
are all largely unaffected by 32/64 bit. It does let your CPU run in it's 
native mode - if there even is such a thing on x86 - and as progress marches 
on regardless so 64 bit is where the focus is these days.

You will find the occasional issue with brain-dead proprietary software 
products (note carefully how I'm NOT looking at Adobe...) but that is fixable 
with nsspuginwrapper.

Reinstall by all mans if it makes you happy. Downtime will be a few hours.
Don't migrate unless you are a toolchain geek and want street cred from being 
able to do it. It's not worth the pain.




>
> Thanks
> Laszlo
>
>
> 2010/9/7 Alan McKinnon <alan.mckinnon@×××××.com>
>
> > Apparently, though unproven, at 17:44 on Tuesday 07 September 2010,
> > SpaceCake
> >
> > did opine thusly:
> > > Hi,
> > >
> > > Is there a user friendly guide or howto to help me to migrate my 32 bit
> > > gentoo to 64 bit without loosing my settings?
> > >
> > > Thank you
> > > Laszlo
> >
> > Forget it, don't even try. You might succeed, but it will not be worth
> > the effort. You will complete the following steps in about half the
> > time:
> >
> > 1. Back up /etc and anything else you want to keep
> > 2. Reinstall
> > 3. Set CHOST to something suitable
> > 4. emerge -e world
> > 5. Restore stuff from step #1
> >
> > It's an interesting exercise to try and do the migration, people who like
> > puzzles enjoy it. If your goal is to have a 64 bit system using the route
> > of
> > least pain, best to follow the path with lots of consensus around here -
> > the
> > one above.
> >
> >
> > --
> > alan dot mckinnon at gmail dot com

-- 
alan dot mckinnon at gmail dot com