Messages in this thread | | | Date | Tue, 15 Apr 2008 23:08:18 +0200 | From | Ingo Molnar <> | Subject | Re: [bug] SLUB + mm/slab.c boot crash in -rc9 |
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* Ingo Molnar <mingo@elte.hu> wrote:
> > * Christoph Lameter <clameter@sgi.com> wrote: > > > On Tue, 15 Apr 2008, Ingo Molnar wrote: > > > > > my current guess would have been some bootmem regression/interaction > > > that messes up the buddy bitmaps - but i just reverted to the v2.6.24 > > > version of bootmem.c and that crashes too ... > > > > The simplest solution for now may be to go with your workaround > > increasing SECTION_SIZE_BITS to 27. [...] > > the bug's effects are so severe that this is the last thing i'd like > to do.
more verbosely: we sometimes do "blind" reverts, if it's reasonably established (or strongly suspected) that a revert makes a bug less severe. We do this even if we dont fully understand the bug and its effects and time runs out - on the assumption that we wont get worse than the old code was.
but what i'd not really like to do are blind _non-revert_ changes. With your suggested change we'd introduce a seemingly innocious but still wholly new (and untested) memory setup layout on the most popular Linux kernel memory config in existence. (!PAE 32-bit is still being run on more than 50% of the Linux desktops - around 80% runs 32-bit kernels.)
And as this bug demonstrates it, seemingly small differences appear to have large effects so we cannot know in what direction that would go - we might turn a rare regression into a common regression. I'd rather release with this bug being unfixed than with tweaking it just because the effect seems less severe on a totally unrepresentative set of systems.
Ingo
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