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    SubjectRe: [PATCH -v2] x86: increase NR_IRQS and nr_irqs
    On 01/03/2010 07:06 PM, Jesse Brandeburg wrote:
    > On Mon, Dec 28, 2009 at 9:08 PM, Yinghai Lu <yinghai@kernel.org> wrote:
    >> have a system with lots of igb and ixgbe, when iov/vf are enabled for
    >> them, we hit the limit of 3064.
    >>
    >> when system have 20 pcie installed, and one card have 2 functions, and one
    >> function need 64 msi-x,
    >> may need 20 * 2 * 64 = 2560 for msi-x
    >> but if iov and vf are enabled
    >> may need 20 * 2 * 64 * 3 = 7680 for msi-x
    >> assume system with 5 ioapic, nr_irqs_gsi will be 120.
    >> NR_CPUS = 512, and nr_cpu_ids = 128
    >> will have NR_IRQS = 256 + 512 * 64 = 33024
    >> will have nr_irqs = 120 + 8 * 128 + 120 * 64 = 8824
    >>
    >> when SPARSE_IRQ is not set, there is no increase with data
    >> when NR_CPUS=128, and SPARSE_IRQ is set
    >> text data bss dec hex filename
    >> 21837444 4216564 12480736 38534744 24bfe58 vmlinux.before
    >> 21837442 4216580 12480736 38534758 24bfe66 vmlinux.after
    >> when NR_CPUS=4096, and SPARSE_IRQ is set
    >> text data bss dec hex filename
    >> 21878619 5610244 13415392 40904255 270263f vmlinux.before
    >> 21878617 5610244 13415392 40904253 270263d vmlinux.after
    >>
    >> -v2: update comments to address Ingo's concern
    >>
    >> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    >
    > I'm not sure this is the best plan, but may be okay for now. What
    > happens when all of your slots have 6 port 82599 ixgbe adapters in
    > them? They are being made[1], as well as quad port 82576 igb
    > adapters, however I'm not fully sure of the SRIOV support of the
    > bridges being used on those adapters.
    >
    > Is it on the table to (re-)design this subsystem to be a little more
    > dynamic? There are probably examples in ppc64 or ia64 directories.
    > Every time you suggest a limit I can find a case where it won't be
    > enough.
    >
    > [1] http://www.hotlavasystems.com/products_10gbe.html

    you mean
    20 * 6 * 64 * 3 ?

    23040

    maybe we can just keep nr_irqs = (256 - 32 - 10) * nr_cpu_ids?
    32: for exception
    10: for IPI etc.

    YH


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