[lkml]   [2009]   [Oct]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: Irq architecture for multi-core network driver.
    David Daney <> writes:

    > Chris Friesen wrote:
    >> On 10/22/2009 03:40 PM, David Daney wrote:
    >>> The main problem I have encountered is how to fit the interrupt
    >>> management into the kernel framework. Currently the interrupt source
    >>> is connected to a single irq number. I request_irq, and then manage
    >>> the masking and unmasking on a per cpu basis by directly manipulating
    >>> the interrupt controller's affinity/routing registers. This goes
    >>> behind the back of all the kernel's standard interrupt management
    >>> routines. I am looking for a better approach.
    >>> One thing that comes to mind is that I could assign a different
    >>> interrupt number per cpu to the interrupt signal. So instead of
    >>> having one irq I would have 32 of them. The driver would then do
    >>> request_irq for all 32 irqs, and could call enable_irq and disable_irq
    >>> to enable and disable them. The problem with this is that there isn't
    >>> really a single packets-ready signal, but instead 16 of them. So If I
    >>> go this route I would have 16(lines) x 32(cpus) = 512 interrupt
    >>> numbers just for the networking hardware, which seems a bit excessive.
    >> Does your hardware do flow-based queues? In this model you have
    >> multiple rx queues and the hardware hashes incoming packets to a single
    >> queue based on the addresses, ports, etc. This ensures that all the
    >> packets of a single connection always get processed in the order they
    >> arrived at the net device.
    > Indeed, this is exactly what we have.
    >> Typically in this model you have as many interrupts as queues
    >> (presumably 16 in your case). Each queue is assigned an interrupt and
    >> that interrupt is affined to a single core.
    > Certainly this is one mode of operation that should be supported, but I would
    > also like to be able to go for raw throughput and have as many cores as possible
    > reading from a single queue (like I currently have).

    I believe will detect false packet drops and ask for unnecessary
    retransmits if you have multiple cores processing a single queue,
    because you are processing the packets out of order.


     \ /
      Last update: 2009-10-23 10:01    [W:0.025 / U:48.636 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site