x32 abi support?

Lennart Poettering mzerqung at 0pointer.de
Wed May 16 14:28:31 UTC 2012


On Wed, 16.05.12 14:31, Matthew Garrett (mjg59 at srcf.ucam.org) wrote:

> On Wed, May 16, 2012 at 09:18:32AM -0400, Neal Becker wrote:
> > I noticed this article:
> > 
> > http://www.phoronix.com/scan.php?page=news_item&px=MTEwMTk
> > 
> > Has this been discussed on fedora?
> 
> x32 is mostly beneficial in that it reduces pointer size and so memory 
> consumption, with the side benefit that it may also provide slightly 
> higher performance due to being able to fit more in cache. But this is 
> only true for a pure x32 system. If you have any applications that need 
> to be 64-bit (ie, anything that is going to need more than 4GB of 
> address space, which is very different from needing more than 4GB of 
> RAM) then you need to have two copies of your libraries and suddenly 
> your memory benefits have entirely vanished.
> 
> So, overall, x32 is only really beneficial for embedded platforms rather 
> than general purpose ones. As Josh says, if there's sufficient interest 
> then it could potentially be implemented as a separate architecture and 
> spend some time in secondary, but I don't know that there'd be a huge 
> benefit to Fedora to spend much time on it.

Mhmm, so I was under the impression that x32 was mostly about increasing
the scalability of virtualized systems. i.e. run a higher number of
x32 containers/VM on an x86_64 host. Most server software that is run in
containers/VMs does not require 64bit address space, and hence using x32
for them should be quite benificial so that you can run more
containers/VMs per host. After all this would reduce memory and CPU
consumption of each, and due to smaller memory usage also result in less
IO?

I'd assume that Fedora is supposed to be suitable to build highly
scalable virtualized hosts, so I'd also assume that x32 should be very
much in focus for us?

Lennart

-- 
Lennart Poettering - Red Hat, Inc.


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