Re: Kernel preemption, yes or no? (was: Filesystem gets a hugeperformance boost)

[Matt Dillon]

:IIRC, didn't the NT driver for some NIC (Intel?) switch to polling,
:anyway, under heavy load?  The reasoning being that you _know_ that you're
:going to get something... why bother an IRQ hit?
:
:That said, IRQ distribution sounds like a good thing for the general case.

    Under a full load polling would work just as well as an interrupt.
    With NT for the network tests they hardwired each NIC to a particular
    CPU.  I don't know if they did any polling or not.

:> If you have one NIC then obviously you can't take multiple interrupts
:> for that one NIC on different cpu's.  No great loss, you generally don't
:> want to do that anyway.
:
:Actually, I should think that one would _want_ to serialize traffic for a
:given NIC.  (I'm ignoring when one trunks NICs... speaking of which,
:anyone have info on 802.3ad? ;-)  Otherwise, one ends up with a race that
:[potentially] screws up packet sequence.
:
:Eddy

    Yes.  Also NICs usually have circular buffers for packets so, really,
    only one cpu can be processing a particular NIC's packets at any given
    moment.

                                        -Matt

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