lkml.org 
[lkml]   [2008]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 0/16 v6] PCI: Linux kernel SR-IOV support
    Anthony Liguori wrote:
    > I don't think it's established that PV/VF will have less latency than
    > using virtio-net. virtio-net requires a world switch to send a group
    > of packets. The cost of this (if it stays in kernel) is only a few
    > thousand cycles on the most modern processors.
    >
    > Using VT-d means that for every DMA fetch that misses in the IOTLB,
    > you potentially have to do four memory fetches to main memory. There
    > will be additional packet latency using VT-d compared to native, it's
    > just not known how much at this time.

    If the IOTLB has intermediate TLB entries like the processor, we're
    talking just one or two fetches. That's a lot less than the cacheline
    bouncing that virtio and kvm interrupt injection incur right now.

    --
    error compiling committee.c: too many arguments to function



    \
     
     \ /
      Last update: 2008-11-16 17:09    [W:0.021 / U:30.084 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site