RFC: Page size on PPC/PPC64 builders

[Dominik 'Rathann' Mierzejewski]

On Sunday, 02 March 2008 at 14:59, David Woodhouse wrote:
> The PPC64 build hosts (which also build ppc32 packages) recently
> switched to RHEL5, and hence have 64KiB page size.
> 
> This is permitted by the PPC ABI, just as it is by the x86_64 ABI, and
> works perfectly well for almost everything.
> 
> Occasionally, however, it shows up some bugs in packages. This week, it
> found bug #435337, which is a generic bug and not really ppc-specific --
> although I won't enter the debate on whether it's a glibc bug or a bug
> with the programs which 'naively' expect pthread_attr_setstacksize() to
> actually set the stack size to the number they provide.
> 
> However, despite the fact that the majority of build failures on PPC
> actually demonstrate _generic_ bugs and not arch-specific bugs at all,
> some packagers don't bother to look -- they prefer to just exclude the
> 'offending' architecture and move on without checking to see what the
> problem is. And mutter to themselves that PPC is 'painful', despite the
> fact that it's helping to improve the quality of Fedora overall by
> finding their generic bugs. Primarily for that reason, I'm tempted to
> switch the PPC builders back to 4KiB pages. 
> 
> I'm not sure it's the right thing to do though -- there are arguments on
> either side.
> 
> For 4KiB pages:
>  - Makes life 'easier' for PPC builds, to stop people whining about it
>    finding their bugs for them.
>  - Consistent with what we actually ship in Fedora.

-1
Packagers' lack of time or laziness is not a good excuse. If they can't
fix it, they should seek help either from the PPC SIG or upstream.

> For 64KiB pages:
>  - Finds real bugs
>  - Consistent with what will be shipped for RHEL.

+1, for the reasons you specified below.

> Note that although some of us might not care so much about RHEL, the
> point about consistency in that case is stronger -- because programs
> _built_ with 64KiB pages are almost always going to work when run with
> 4KiB pages, but the other way round is not so frequently true.
> 
> I'm concerned that switching back to 4KiB pages is just papering over
> real bugs to make life easier for PPC folks. I suspect that what I
> should _actually_ do is keep it 64KiB, brazen it out and LART people who
> just exclude ppc builds without actually looking at the problem for
> themselves. But I'm lazy too... maybe we should switch the x86_64
> builders to 64KiB instead? :)

I'm game. ;)

Regards,
R.

-- 
Fedora contributor http://fedoraproject.org/wiki/DominikMierzejewski
Livna contributor http://rpm.livna.org MPlayer developer http://mplayerhq.hu
"Faith manages."
        -- Delenn to Lennier in Babylon 5:"Confessions and Lamentations"