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@xxxxxxxxxx> - 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 -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
