[LSF/MM TOPIC][LSF/MM ATTEND] NAPI polling for block drivers

[Sagi Grimberg]

> --
> [1]
> queue = b'nvme0q1'
>      usecs               : count     distribution
>          0 -> 1          : 7310 |****************************************|
>          2 -> 3          : 11       |      |
>          4 -> 7          : 10       |      |
>          8 -> 15         : 20       |      |
>         16 -> 31         : 0        |      |
>         32 -> 63         : 0        |      |
>         64 -> 127        : 1        |      |
>
> [2]
> queue = b'nvme0q1'
>      usecs               : count     distribution
>          0 -> 1          : 7309 |****************************************|
>          2 -> 3          : 14       |      |
>          4 -> 7          : 7        |      |
>          8 -> 15         : 17       |      |
>

Rrr, email made the histograms look funky (tabs vs. spaces...)
The count is what's important anyways...

Just adding that I used an Intel P3500 nvme device.

> We can see that most of the time our latency is pretty good (<1ns) but with
> huge tail latencies (some 8-15 ns and even one in 32-63 ns).

Obviously is micro-seconds and not nano-seconds (I wish...)