CPU load under heavy traffic

Hi,

we ran today some performance tests and were surprised by the high CPU usage due to the WiFi traffic.

We wondered if other people observe similar values, and whether there is some tuning/settings not quite right on our system.

Setup:

   - custom PCB using Murata 1DX (BCM4343W)

   - SoC: i.MX6SL Cortex A9, 1GHz (running at full clock rate)

   - Test software: iperf3

  - 1DX acting as an P2P-GO

  - Linux PC connected to P2P-GO (located close to 1DX)

The traffic throughput varies between 6 Mbps and 40 Mbps.

The CPU usage on the iMX is at around 30%, mainly by thread "ksdioirq/mmc2" (other WiFi thread, like "dhd_dpc" and "dhd_watchdog" take low single digit percentage of CPU).

Would you expect 30% CPU for the sdio thread for just moving a maximum of 40 Mbps ... ?!

Thx

Raul

PS: during boot, it claims the SDHC driver that it will use DMA.