Re: RH9 Compatibility

[fluke gibson mw luc edu]

On Sun, 30 Mar 2003, Max Z. wrote:

> I have a few questions concerning the upcoming RedHat Linux 9.0 release:
> 
> 1. Due to the implementation of the new threading tech, would I be able to
> recompile redhat included kernel? 

Oddly worded question... the new threading model will not make it easier 
to recompile the redhat included kernel.  Rather, it is due to the SRPM of 
the kernel that is provided in compliance with the GPL which allow you to 
be able to recompile the kernel.

> 2. Would I be able to compile and run non-redhat kernels with out loosing
> the new threading tech? 

I believe there is three areas where the threading model is "improved" in 
RH9:

1) Newer version of glibc
2) Support for hyperthreading processors
3) Improved schedular backported from 2.5 kernel series

The newer version of glibc will continue to be a newer version regardless 
of what kernel you run.

Hyperthreading is only provided if you have a processor that supports it.  
On the majority of laptop processors, you should not loose anything by 
booting a kernel that isn't hyperthreading aware just as you won't loose 
anything by booting an uni-processor kernel instead of a SMP kernel.

If you switch to a kernel without the improved schedular such as the 
standard 2.4.20 kernel then threaded apps should continue to work but the 
system will not have any performance advantages that an improved schedular 
will provide.  It is debate-able if the schedular would make a human 
noticable difference on a laptop machine used as a workstation.  Tweaking 
the "nice" levels of the processes may provide better results in a 
non-server enviroment.

> 3. How is the threading implementation different from the 2.5 development
> kernel? 

The improved schedular was back-ported from a 2.5 series kernel but is 
intended to be a semi-stable snapshot.  The 2.5 series will continue to be 
developed for better or worse until a kernel feature freeze is called and 
then only minor bug changes will be added.  At least in theory.  RedHat 
may see a need to move to a newer snapshot of the schedular.  Likewise, 
the rules of what gets frozen with standard kernel development where bent 
during the 2.4.x kernel series to fix the VM.

> 4. Is the threading implementation a patch on top of the 2.4.20 kernel? 

Yes.  At least mostly.  The RawHide kernel includes around 150 patches
including the 2.4.21-pre3 patch.

> 5. If I will run a 2.5 development kernel, will redhat work the same in
> terms of threading?

Theoritically, the function calls will be handled similarily enough that 
the programs will appear to run the same.  In practice, the 2.5 kernel 
series may introduce bugs or enhance the kernel thread support.

> 6. Would I be able to run NVIDIA drivers if I compile them from source? 

I believe RH9 ships with XFree 4.2 instead of RH8's XF4.1.  X server 
modules which compiled from source on RH8 may not support the XFree 4.2.

> 7. Would Java Runtime Environment work? 

It would be desirable to use a JRE which is compiled with the newer
version of glibc and gcc.  Kaffe should compile and install fine on RH9.  
It is highly likely that during April either Blackdown, IBM or possibly
Sun/Javasoft will release a JRE/JDK for RH9.

> 8. What other incompatibilities are introduced?

RH9 will provide the usual compat RPMs if you wish to attempt backward 
binary compatiablity.  There are potental binary and source 
incompatiblities in areas where the libraries have been upgraded (glibc, 
Qt, Gtk, etc).  Also, the newer g++ may (or may not) have again modified 
the ABI.

Just as with moving from RH7 to RH8, RH9 provides Apache v2 which is not 
binary or source compatable with Apache v1 modules which where used on 
RH7.  At least the RH9 apache devel package should provide the instdo.sh 
script.

> 9. Considering that redhat does not support ACPI functions, would they
> work if they are enabled in the kernel? (I will be running it on a
> laptop)

If you have a laptop that *correctly* impliments ACPI and are not using an 
pcmcia cards which cause problems then feel free to build a kernel which 
supports ACPI.  I'm not sure what human noticable difference you expect to 
get over APM.  One of the biggest battery eaters can be solved with hdparm 
regardless of kernel APM/ACPI support.

> Your answers are greatly appreciated. I will use this info to determine if I
> should buy a copy of Redhat 9 or if I should wait.

If your using RH 7.3 and your happy with RH 7.3 then you should wait until
October for RH 9.1.  If your running RH 8 or want additional functionality 
that RH 7.3 doesn't provide then upgrade to RH9.

Personally, I buy a copy regardless of when I'm going to install it.  I
find it is always nice to have a bootable CD with the latest version of
Anaconda in case I need to boot into rescue mode.