Re: HEADS-UP: IFLIB implementations of sys/dev/e1000 em, lem, igb pending

On Thu, Jan 12, 2017 at 1:54 AM, Matthew Macy <mmacy_at_nextbsd.org> wrote:

>  >  A flame graph for the core cycle count and a flame graph with cache
> miss stats from pmc would be a great start.
>  >
>  >
>  > ​I didn't know the exact event name to use for cache miss stats, but
> here are the flame graphs for CPU_CLK_UNHALTED_CORE:
>  > http://dev.bsdrp.net/netgate.r311848.CPU_CLK_UNHALTED_CORE.svg
>  > http://dev.bsdrp.net/netgate.r311849.CPU_CLK_UNHALTED_CORE.svg
>
> Thanks. Having twice as many txqs would definitely help. It's also clear
> that there may be some sort of peformance issue in iflib_txq_drain.
> Although it could just be non-stop cache misses on the packet headers.
>
>
> ​Any news about the performance issue in iflib_txq_drain ?

On a different hardware (PC Engine APU2), I've got -20% performance drop:

x head r311848: packets per second
+ head r311849: packets per second
+--------------------------------------------------------------------------+
| ++                                                                      x|
|+++                                                                 x xx x|
|                                                                     |_A_||
||A|                                                                       |
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   5        580021        588650        585676      585406.1     3550.8673
+   5        463865        467599        465428      465638.6     1437.9347
Difference at 95.0% confidence
        -119768 +/- 3950.78
        -20.4589% +/- 0.558328%
        (Student's t, pooled s = 2708.9)
​

​Because it's an AMD processor I didn't found the pmc equivalent of
CPU_CLK_UNHALTED_CORE, then I've used BU_CPU_CLK_UNHALTED but I've no idea
if it's the good one.

http://dev.bsdrp.net/apu2.r311848.BU_CPU_CLK_UNHALTED.svg
http://dev.bsdrp.net/apu2.r311849.BU_CPU_CLK_UNHALTED.svg
​
​Thanks​