On Mon, 21 Apr 2003, Nakajima, Jun wrote:
> BTW, I think a better way is to switch from IRQ-base to vector-base.
> We are working on PCI MSI (Messaged Signaled Support) support, and MSI
> does not require IRQ (or the platform does not provide IRQ at all), and
> found a vector-based solution was simpler.
>
> Even if MSI is not required, I think vector-based is a clearer solution
> (IA-64 is using vector-based). IRQs are given by the platform, and the
> kernel cannot do anything with those. Vector assignment/allocation are
> fully controlled by the kernel, and the kernel can return the vector
> number instead of IRQ (except legacy drivers where IRQs < 16).
>
> We made a prototype that simply returns the vector numbers for IRQ to
> device drivers (dev.irq). The function do_IRQ(), for example, gets the
> vector number, instead of IRQ. No changes to arch/i386/kernel/irq.c were
> required.
I know there are more people who want to get rid of NR_IRQS e.g. due to
very sparse irq distribution. For one of the platforms i'm interested in,
we have to make a clear distinction between irqs and vectors so that we
can have seperate vector allocations per interrupt handling domain. I
believe IA-64 does the same but instead per cpu (our domain/node consists
of 4 cpus) NR_IRQS gets in the way due to it being set at 224 when we actually
can service NR_IRQ_VECTORS * NUM_MAXNODES I/O vectors. Can you post your
patch?
Also what MSI devices are you using?
> Before (IRQ-based)
> # cat /proc/interrupts
> CPU0 CPU1
> 0: 10921 671640 IO-APIC-edge timer
> 2: 0 0 XT-PIC cascade
> 9: 0 0 IO-APIC-level acpi
> 14: 5102 1 IO-APIC-edge ide0
> 15: 10 1 IO-APIC-edge ide1
> 16: 0 0 IO-APIC-level uhci-hcd, uhci-hcd
> 18: 449 0 IO-APIC-level uhci-hcd
> 19: 61 0 IO-APIC-level uhci-hcd
> 20: 345 0 IO-APIC-level eth0
> 23: 0 0 IO-APIC-level ehci-hcd
> NMI: 0 0
> LOC: 680526 680437
> ERR: 0
> MIS: 0
>
> After (vector-based)
> CPU0 CPU1
> 0: 709682 0 IO-APIC-edge timer
> 2: 0 0 XT-PIC cascade
> 9: 0 0 IO-APIC-level acpi
> 14: 4988 1 IO-APIC-edge ide0
> 15: 10 1 IO-APIC-edge ide1
> 177: 78 0 IO-APIC-level uhci-hcd
> 185: 0 0 IO-APIC-level uhci-hcd, uhci-hcd
> 193: 58 0 IO-APIC-level uhci-hcd
> 201: 0 0 IO-APIC-level ehci-hcd
> 209: 356 0 IO-APIC-level eth0
> NMI: 0 0
> LOC: 707613 707524
> ERR: 0
> MIS: 0
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This archive was generated by hypermail 2b29 : Wed Apr 23 2003 - 22:00:29 EST