Messages in this thread | | | Date | Thu, 24 Apr 2008 09:36:52 +1000 | From | David Chinner <> | Subject | Re: x86: 4kstacks default |
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On Wed, Apr 23, 2008 at 03:27:01PM +1000, Benjamin Herrenschmidt wrote: > On Sat, 2008-04-19 at 16:23 +0200, Ingo Molnar wrote: > > * Andrew Morton <akpm@linux-foundation.org> wrote: > > > > > > config 4KSTACKS > > > > bool "Use 4Kb for kernel stacks instead of 8Kb" > > > > - depends on DEBUG_KERNEL > > > > depends on X86_32 > > > > + default y > > > > > > This patch will cause kernels to crash. > > > > what mainline kernels crash and how will they crash? Fedora and other > > distros have had 4K stacks enabled for years: > > > > $ grep 4K /boot/config-2.6.24-9.fc9 > > CONFIG_4KSTACKS=y > > > > and we've conducted tens of thousands of bootup tests with all sorts of > > drivers and kernel options enabled and have yet to see a single crash > > due to 4K stacks. So basically the kernel default just follows the > > common distro default now. (distros and users can still disable it) > > Do we routinely test nasty scenarii such as a GFP_KERNEL allocation deep > in a call stack trying to swap something out to NFS ?
I doubt it, because this is the place that a local XFS filesystem typically blows a 4k stack (direct memory reclaim triggering ->writepage). Boot testing does nothing to exercise the potential paths for stack overflows....
Cheers,
Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group
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