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== Comments and Discussion == | == Comments and Discussion == | ||
=== Won't this break OLPC/XO support? === | |||
No, that should work with the i686 kernel and i686 userspace. | |||
=== What about the i586 users? === | |||
Fedora is about bringing the best and latest in free and open source software; concentrating on older CPUs doesn't really fit that forward-looking mission. Moreover, looking at the [http://smolt.fedoraproject.org/static/stats/stats.html | smolt stats] shows only 130 registered i586 systems (as of 2009-01-28); that's less than one twentieth of one percent of registered users. | |||
Revision as of 21:27, 28 January 2009
ArchitectureSupport
Summary
Change what architectures Fedora supports, and what Fedora provides on those architectures.
Owner
- Name: Bill Nottingham
- Name: Jakub Jelinek
- Name: Kyle McMartin
- email: notting@redhat.com, jakub@redhat.com, kmcmartin@redhat.com
Current status
- Targeted release: Fedora 11
- Last updated: 2009-01-28
- Percentage of completion: 0%
Detailed Description
For Fedora 11, we'd like to revisit what architectures Fedora supports, and change some of our defaults so that we work better on those architectures.
The main user-visible changes would be:
- 32-bit x86 would be built for i686 by default. 586-compatible processors would no longer be supported.
- The x86_64 kernel would be installed on compatible hardware, even when installing a 32-bit OS
- The PAE kernel would be installed on other 32-bit hardware, where it is supported
The 32-bit LiveCD would remain using a 32-bit kernel, in all likelyhood.
Benefit to Fedora
By clearly defining what architectures and CPUs we support, we eliminate user confusion about our target.
By optimizing better for those architectures, we give better performance to our users.
By using the x86_64 kernel where appropriate, we allow the kernel to perform better and handle memory better.
By using the PAE kernel where appropriate, we allow features like ExecShield to be used.
By changing the minimum kernel for glibc, we allow the removal of various hacks, tests, and workarounds in the glibc code.
Scope
- The default 32-bit x86 target in koji would be changed from i386 to i686
- mash and pungi would be changed to ship the x86_64 kernel on 32-bit x86
- yum and anaconda would need changes to select the proper kernel
- anaconda will need an override to install the 32-bit kernel on x86_64 hardware, if for no other reason than to be able to test the 32-bit kernel
- syslinux/isolinux may need changes to boot the proper kernel for the installer
- The default compiler flags for gcc in redhat-rpm-config would be changed as follows:
- i386: -march=i586 -mtune=generic
- s390x: -march=z9-109 -mtune=z10
- The required kernel for glibc would be changed to 2.6.18
- binutils for ix86 would be compiled to support x86_64 output
- The compiler would be modifed in some way so that x86_64 output would be available on a 32-bit install, in case kernel modules are needed to be rebuilt
How To Test
Boot Fedora on supported hardware. Make sure it boots and nothing dies with SIGILL. Particular care should go to testing XO hardware, as it's likely to be the least capable CPU supported.
Install 32-bit Fedora on x86_64 hardware. Make sure the x86_64 kernel is installed.
Install 32-bit Fedora on PAE-supporting 32-bit hardware (in other words: Pentium II/III/4, or Atom.) Make sure the PAE kernel is the default.
Additional testing could benchmark apps to see any difference in code size and app speed.
User Experience
Users of x86_64 hardware should notice a better experience in that they are running a kernel that no longer has to worry about low memory, high memory, etc.
Users of the x86 distribution should notice slight speed improvements.
Dependencies
No external dependencies outside the changes listed in Scope.
Contingency Plan
For compiler flags and default RPM architecture: if we need to change after the mass rebuild, we'd need another mass rebuild.
For x86_64-on-32: do not ship x86_64 on 32-bit x86, only ship 32-bit kernels.
For PAE-on-32: default to the normal i686 kernel, with PAE an option.
Documentation
None specifically.
Release Notes
In Fedora 11, the following changes have been made to architecture support:
- i586 CPUs are no longer supported. Fedora requires at least a i686 compatible CPU.
- By default, the x86_64 kernel will be installed and used on compatible hardware, even when installing a 32-bit operating system
- By default, the PAE kernel will be used on 32-bit hardware, where appropriate
Comments and Discussion
Won't this break OLPC/XO support?
No, that should work with the i686 kernel and i686 userspace.
What about the i586 users?
Fedora is about bringing the best and latest in free and open source software; concentrating on older CPUs doesn't really fit that forward-looking mission. Moreover, looking at the | smolt stats shows only 130 registered i586 systems (as of 2009-01-28); that's less than one twentieth of one percent of registered users.