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    SubjectRe: [patch] e1000 TSO parameter
    [Scott, somehow I never received your original response so I'm
    replying based on what I saw in the linux.kernel newgroup...]

    Scott> Do you have any data to share?

    Sure, I don't see why not. Here are the number I got:

    TSO disabled:

    $ modprobe InterruptThrottleRate=0,0,0,0 TSO=0,0,0,0
    $ netperf -l 30 -c -C -H foobar -- -s64K -S64K
    TCP STREAM TEST to foobar
    Recv Send Send Utilization Service Demand
    Socket Socket Message Elapsed Send Recv Send Recv
    Size Size Size Time Throughput local remote local remote
    bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB

    131070 131072 131072 30.00 897.16 34.07 35.00 3.111 3.196

    TSO enabled:

    $ modprobe InterruptThrottleRate=0,0,0,0 TSO=1,1,1,1
    $ netperf -l 30 -c -C -H foobar -- -s64K -S64K
    TCP STREAM TEST to foobar
    Recv Send Send Utilization Service Demand
    Socket Socket Message Elapsed Send Recv Send Recv
    Size Size Size Time Throughput local remote local remote
    bytes bytes bytes secs. 10^6bits/s % S % S us/KB us/KB

    131070 131072 131072 30.00 894.09 11.65 34.48 1.068 3.159

    This looks roughly like you'd expect: with TSO, slightly lower
    throughput but much less CPU overhead.

    With ftp, things get stranger: fetching a 2GByte file via ftp get
    (from the remote end):

    TSO disabled:

    ftp> get big.iso /dev/null
    local: /dev/null remote: big.iso
    200 PORT command successful.
    150 Opening BINARY mode data connection for 'big.iso' (2038628352 bytes).
    226 Transfer complete.
    2038628352 bytes received in 18.17 secs (109554.5 kB/s)

    ftp server CPU utilization: ~ 40%

    With TSO enabled:

    ftp> get big.iso /dev/null
    local: /dev/null remote: big.iso
    200 PORT command successful.
    150 Opening BINARY mode data connection for 'big.iso' (2038628352 bytes).
    226 Transfer complete.
    2038628352 bytes received in 21.16 secs (94070.2 kB/s)

    ftp server CPU utilization: ~ 15%

    So we get almost 15% of throughput drop. This was with plain "netkit
    fptd". AFAIK, it does a simple read/write loop (not sendfile()).

    --david
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