Messages in this thread | | | Date | Mon, 11 Jun 2007 10:36:45 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] move the kernel to 16MB for NUMA-Q |
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Dave Jones wrote: > > FWIW, waay back when (sometime last year if memory serves) > Linus suggested changing the default to 0x1000000 for all x86. > The reasoning was some performance microoptimisation regarding > 4MB aligned TLBs iirc. > > The details have long since evaded my memory, but as an experiment, > I made the change to the Fedora kernel. FC5,FC6 and F7 have been > this way for a while now, with no obvious problems. Ditto RHEL5. > We did get some performance numbers at the time of the change, > but they weren't amazing (basically in the noise). > Given it never seemed to actually get worse, I never got around > to reverting it.. >
Picking the 16 MB base is a bit obnoxious on small-memory machines, 4 MB would probably be a more reasonable base. Of course, 16 MB would avoid the issue of the handful of machines with memory holes at 15-16 MB.
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