On Thu, 2007-02-08 at 14:04, Keith Owens wrote: > Zou Nan hai (on 08 Feb 2007 11:28:44 +0800) wrote: > >Pin ar.kr2 of each CPU, so that smp_processor_id can use it. > > Historically ar.k2 has been reserved for debugging purposes, for > example in ivt.S. Debuggers often need a location that can be used to > track progress, it has to be somewhere that does not rely on TLB > entries and is guaranteed to appear in MCA/INIT records - ar.k2 is > perfect for this. > Ok, seems that current kr3 is only used by ia64_itc_printk_clock? > Use Tony's suggestion of testing for a change in ar.k3 (guaranteed to > be unique on every cpu) and caching the corresponding cpu number when > it changes. > But why do we even need to cache it? It is already in a register if we put it to kr3. so smp_processor_id() could be very fast. and later sys_getcpu can also be very fast. Thanks Zou Nan hai > - > To unsubscribe from this list: send the line "unsubscribe linux-ia64" > in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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