Re: [PATCHSET 0/3] Improve MSG_RING SINGLE_ISSUER performance

[Jens Axboe <axboe@kernel.dk>]

On 5/28/24 12:31 PM, Jens Axboe wrote:
> I suspect a bug in the previous patches, because this is what the
> forward port looks like. First, for reference, the current results:

Got it sorted, and pinned sender and receiver on CPUs to avoid the
variation. It looks like this with the task_work approach that I sent
out as v1:

Latencies for: Sender
    percentiles (nsec):
     |  1.0000th=[ 2160],  5.0000th=[ 2672], 10.0000th=[ 2768],
     | 20.0000th=[ 3568], 30.0000th=[ 3568], 40.0000th=[ 3600],
     | 50.0000th=[ 3600], 60.0000th=[ 3600], 70.0000th=[ 3632],
     | 80.0000th=[ 3632], 90.0000th=[ 3664], 95.0000th=[ 3696],
     | 99.0000th=[ 4832], 99.5000th=[15168], 99.9000th=[16192],
     | 99.9500th=[16320], 99.9900th=[18304]
Latencies for: Receiver
    percentiles (nsec):
     |  1.0000th=[ 1528],  5.0000th=[ 1576], 10.0000th=[ 1656],
     | 20.0000th=[ 2040], 30.0000th=[ 2064], 40.0000th=[ 2064],
     | 50.0000th=[ 2064], 60.0000th=[ 2064], 70.0000th=[ 2096],
     | 80.0000th=[ 2096], 90.0000th=[ 2128], 95.0000th=[ 2160],
     | 99.0000th=[ 3472], 99.5000th=[14784], 99.9000th=[15168],
     | 99.9500th=[15424], 99.9900th=[17280]

and here's the exact same test run on the current patches:

Latencies for: Sender
    percentiles (nsec):
     |  1.0000th=[  362],  5.0000th=[  362], 10.0000th=[  370],
     | 20.0000th=[  370], 30.0000th=[  370], 40.0000th=[  370],
     | 50.0000th=[  374], 60.0000th=[  382], 70.0000th=[  382],
     | 80.0000th=[  382], 90.0000th=[  382], 95.0000th=[  390],
     | 99.0000th=[  402], 99.5000th=[  430], 99.9000th=[  900],
     | 99.9500th=[  972], 99.9900th=[ 1432]
Latencies for: Receiver
    percentiles (nsec):
     |  1.0000th=[ 1528],  5.0000th=[ 1544], 10.0000th=[ 1560],
     | 20.0000th=[ 1576], 30.0000th=[ 1592], 40.0000th=[ 1592],
     | 50.0000th=[ 1592], 60.0000th=[ 1608], 70.0000th=[ 1608],
     | 80.0000th=[ 1640], 90.0000th=[ 1672], 95.0000th=[ 1688],
     | 99.0000th=[ 1848], 99.5000th=[ 2128], 99.9000th=[14272],
     | 99.9500th=[14784], 99.9900th=[73216]

I'll try and augment the test app to do proper rated submissions, so I
can ramp up the rates a bit and see what happens.

-- 
Jens Axboe