On Tuesday 02 May 2006 08:57, Eric W. Biederman wrote: > Andi Kleen <ak@xxxxxxx> writes: > > >> >- Modify do_IRQ to get passed an interrupt vector# from the > >> > interrupt vector instead of an irq number, and then lookup > >> > the irq number in vector_irq. This means we don't need > >> > a code stub per irq, and allows us to handle more irqs > >> > by simply increasing NR_IRQS. > >> > >> isn't the vector number already on the stack from > >> ENTRY(interrupt) > >> pushl $vector-256 > > > > Yes - and interrupts/vectors are currently always identical. > > No. At best there is a fixed offset. They can't be > identical because the first 32 vectors are reserved, > for processor exceptions. > > Beyond that the kernel would not need the vector_irq and irq_vector > arrays if they were always identical, or even if they were one to one. Yes I should have said it's a fixed offset. Sorry for the confusion. Just no mapping table needed. > > If you look at assign_irq_vector you will see that by default we > allocate every 8th vector. Looking at the comment in > init_IO_APIC_traps() this seems to be because we want to avoid > apic bugs with multiple interrupts of the same priority. > Although why we skip 8 instead of 16 is beyond me. Hmm - i guess that's old APIC bugs. Might be worth revisiting on 64bit. > > Although now that I think about it, using some assembler macros > instead of cpp macros could probably solve the problem more easily > than generating the stubs at runtime. I think the worst case is > 256 cpus * 32 irqs per cpu 32 irqs? It's (255-32) > * 10 bytes per stub = 80K. My calculations gave >200k which is definitely too much. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
