rawhide report: 20050706 changes

Dave Jones davej at redhat.com
Wed Jul 6 17:09:30 UTC 2005


On Wed, Jul 06, 2005 at 07:26:59AM -0500, Ian Pilcher wrote:
 > Arjan van de Ven wrote:
 > >On Wed, 2005-07-06 at 07:13 -0400, Build System wrote:
 > >
 > >>- Drop x86-64 SMP kernels, and make generic kernel use SMP.
 > >why is this??
 > 
 > Presumably it's because so many processors these days are either Hyper-
 > Threaded or (soon) dual-core.  At some point, the benefit of building
 > and shipping uni-processor kernels is less than the cost.

Indeed.  The proportion of UP vs SMP x86-64's out there is only
going to increase in favour of SMP.  Last numbers I read showed
that HT EM64T's outsold AMD64's already.  As the UP kernel gets
less and less testing moving forward, it doesn't really offer
any great benefit to shipping it. Especially as the performance
overheads of running SMP locking on UP is negligable.

Finally, there's going to be an extra set of kernels for x86-64 xen
at some point, which pushes the total number of kernels up yet again.
As we're constantly battling for CD space, this tradeoff seemed worth it.

If test1 goes out, and it blows up horribly (ie, there are lots of
single CPU x86-64 boxes out there which can't run the SMP kernel)
we'll look at reconsidering this decision.  Given x86-64 doesn't have
the crappy lineage that it's 32bit predecessor has, I'm confident that
this won't be the case.

		Dave




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