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SubjectRe: [PATCH 00/16] dyn_array and nr_irqs support v2
On Fri, Aug 1, 2008 at 1:46 PM, Eric W. Biederman <> wrote:
> Yinghai Lu <> writes:
>> Please check dyn_array support for x86
> YH you have not addressed any of my core concerns and this exceeds my review limit.

i mean drivers/serial/8250.c

> Unfortunately I don't feel like this is a productive process.
> My core concerns are:
> - You have not separated out and separately pushed the regression patch. So that we can
> fix the current rc release. Simply tuning NR_IRQS is all I feel comfortable with for
> fixing things in the post merge window period.

Increase NR_IRQS to 512 for x86_64?

> - The generic code has no business with dealing with NR_IRQS sized arrays.
> Since we don't have a generic problem I don't see why we should have a generic dyn_array solution.

arch/x86/kernel/io_apic_32.c:DEFINE_DYN_ARRAY(irq_2_pin, sizeof(struct
irq_pin_list), pin_map_size, 16, NULL);
sizeof(struct balance_irq_affinity), nr_irqs, PAGE_SIZE,
arch/x86/kernel/io_apic_32.c:DEFINE_DYN_ARRAY(irq_vector, sizeof(u8),
nr_irqs, PAGE_SIZE, irq_vector_init_work);
arch/x86/kernel/io_apic_64.c:DEFINE_DYN_ARRAY(irq_cfg, sizeof(struct
irq_cfg), nr_irqs, PAGE_SIZE, init_work);
arch/x86/kernel/io_apic_64.c:DEFINE_DYN_ARRAY(irq_2_pin, sizeof(struct
irq_pin_list), pin_map_size, sizeof(struct irq_pin_list), NULL);

per_cpu__kstat.irqs, sizeof(unsigned int), nr_irqs, sizeof(unsigned
long), NULL);

and kstat.irqs is the killer... every cpu will have that. [NR_CPUS][NR_IRQS]...

> - The dyn_array infrastructure does not provide for per numa node allocation of
> irq_desc structures, limiting NUMA scalability.

you plan to move irq_desc when irq_affinity is set to cpus on other node?

something like DEFINE_PER_NODE_DYN_ARRAY ?

> - You appear to be papering over problems instead of digging in and actually fixing them.

use dyn_array is less intrusive at this point. and dyn_array related
code is not big.
just NR_IRQS to nr_irqs to make the patches more bigger. actually it is simple.

with acpi_madt probing, nr_irqs is much small. like 48 or 98. and
current one is MACRO 224 or 256.

> YH Here is what I was suggesting when the topic of killing NR_IRQs came up a week or so
> ago.
> Which essentially boils down to:
> - Removing NR_IRQS from the non-irq infrastructure code.
> - Add a config option for architectures that are not going to use an array
> - In the genirq code have a lookup function that goes from irq number to irq_desc *.

so we need one pointer array with that lookup function? what is the
pointer array index size?
or use list in that lookup function?

how about percpu kstat.irqs?

> The rest we should be able to handle in a arch dependent fashion.
> When we are done we should be able to create a stable irq number for msi interrupts
> that is something like: bus:dev:fun:vector_no which is 8+5+3+12=28 bits long.

how about irq migration from one cpu to another with different vector_no ?


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