Luck, Tony wrote: >> include/asm/hardirq.h:30:3: #error HARDIRQ_BITS is too low! > > This one is a direct consequence of the new definition of NR_IRQS: > > #define NR_IRQS (NR_VECTORS + 32 * NR_CPUS)) > > With a large NR_CPUS value, this gets too big. Do we really need to scale > it with the number of cpus? I don't think this is the right thing to do. > While large cpu count systems may also have a large number of I/O devices, > the two parameters aren't strongly connected. > > We could prevent it blowing up by doing: > > /* NR_IRQS is limited by HARDIRQ_BITS */ > #if (NR_VECTORS + 32 * NR_CPUS)) < 16363 > #define NR_IRQS (NR_VECTORS + 32 * NR_CPUS)) > #else > #define NR_IRQS 16383 > #endif I think if the number of CPUs is small, the value of NR_IRQS depends on the value of NR_CPUS. But, if the number of CPUs is large, this relation becomes weak. Because, in general machine composition, the number of I/O devices doesn't increase proportionally even if the number of CPUs increases. So, this threshold such as 16383 is too large. I'd like to define NR_IRQS as follows. #if (NR_VECTORS + 32 * NR_CPUS)) < 1024 #define NR_IRQS (NR_VECTORS + 32 * NR_CPUS)) #else #define NR_IRQS 1024 #endif And, I will make NR_IRQS a tunable parameter which user can define as boot parameter. Thanks, Yasuaki Ishimatsu > > But that looks rather ugly and still fails to build because of overflow of the percpu area. > This gets big because of include/linux/kernel_stat.h: > > DECLARE_PERCPU(struct kernel_stat, kstat); > > With the current allocation of percpu stuff, it looks like we can push NR_IRQS up > to around 7.5K, but that would leave no space for other additions to percpu space. > So if large systems are going to need as many as 7.5K IRQs, then we'll also need to > do something about kstat. > > -Tony > - > 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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