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And there is no >>>> penalty for migration. >>> This code looks like it relies on 'page zero' already being percpu. >>> So it probably isn't really that different. >>> Some values like the 'preemption disable count' and 'current' could be >>> (maybe are?) written into page zero to give fast access. >> I don't quite get what you mean about 'page zero'. > 'page zero' is (at least for some cpu) the memory that can be accessed > using a small offset embedded in the instruction. > This is equivalent to using offsets from an 'always zero' %r0. > > The code relies on the accesses to 960(%r0) being per-cpu. Thank you. Heiko also elaborated it. Yang > > -- David