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    SubjectRe: Gigabit Performance 2.4.19-preX - Excessive locks, calls, waits
    > > Thats up to the network adapter. In fact the Linux drivers mostly do 
    > > keep preloaded with full sized buffers and only copy if the packet size
    > > is small (and copying 1 or 2 cache lines isnt going to hurt anyone)
    > There's an increase in latency. For my application, I have no

    A very tiny one (especially if you keep a small buffer pool around too).
    To copy a packet is 2 cache line loads, which will dominate, some
    writes that you wont be able to measure, and a writeback you won't be
    able to instrument without a bus analyser.

    For receive paths its up to the driver. The copy to smaller buffer is
    something the driver can choose to do. It and it alone decide what skbuff
    to throw at the kernel core

    The bigger ring helping is interesting but itself begs a question. Do you
    ever dirty rather than merely reference skbuff data. In that case a bigger
    ring may simply be hiding the fact that the recycled skbuff has dirty
    cached data that has to be written back. Does the combination of hardware
    you have do the right thing when it comes to the invalidating - and do
    you ever DMA into a partial cache line ?

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      Last update: 2005-03-22 13:24    [W:0.020 / U:123.192 seconds]
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