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Date: Tue, 15 Apr 2008 23:08:18 +0200 From: Ingo Molnar <mingo@...e.hu> To: Christoph Lameter <clameter@....com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Pekka Enberg <penberg@...helsinki.fi>, linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...e.de>, Andrew Morton <akpm@...ux-foundation.org>, "Rafael J. Wysocki" <rjw@...k.pl>, Yinghai.Lu@....com, apw@...dowen.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Subject: Re: [bug] SLUB + mm/slab.c boot crash in -rc9 * Ingo Molnar <mingo@...e.hu> wrote: > > * Christoph Lameter <clameter@....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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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