Messages in this thread | | | Date | Tue, 26 Aug 2008 15:28:48 -0400 | From | Dave Jones <> | Subject | Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected |
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On Tue, Aug 26, 2008 at 12:09:46PM -0700, Linus Torvalds wrote:
> If you want the default kernel to support 4k cores, we'll need to fix the > stack usage. I don't think that is impossible, but IT IS NOT GOING TO > HAPPEN for 2.6.27. > > And quite frankly, if some vendor like RedHat enables NR_CPUS=4096 by > default, they are totally and utterly crazy.
heh. *picks through Fedora changelog*
* Thu Aug 14 2008 Dave Jones <davej@redhat.com> - Bump max cpus supported on x86-64 to 4096. Just to see what happens.
I never did get to find out unfortunatly, because of the security fiasco in Fedora infrastructure the last week or two.
> But some SGI-specific binary that is meant for SGI machines only, and has > been extensively tested with the setup used on SGI machines is a different > thing.
Every extra kernel image a distro vendor ends up shipping has an associated cost.
* build time: It currently takes about 2 hours for a set of Fedora RPMs. For RHEL it'll be even worse due to the extra archs). Killing off -smp specific builds was a big win for us in this regard. Adding extra flavours is always painful.
* diskspace (distro kernels aren't small. With the associated debugging symbols, they take up a shitload of disk space really fast).
* Having everyone running the same kernel makes it much easier to test/debug. Our QA guys hate adding extra columns to their test matrix.
But yes, for this to be even remotely feasible, there has to be a negligable performance cost associated with it, which right now, we clearly don't have. Given that the number of people running 4096 CPU boxes even in a few years time will still be tiny, punishing the common case is obviously absurd.
Dave
-- http://www.codemonkey.org.uk
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