Trouble shooting low rate MCS9 in 802.11ac

[Vu Hai NGUYEN]

>> My 2 devices have an ARM processor 1200MHz.
>> If I connect these two devices by an Ethernet cable and doing iperf (in TCP)
>> I can obtain 880 Mbps, it means that my processor can deal with that speed
>> of data transfer. But if I use Wi-fi instead of Ethernet to test rate between these
>> devices, my processor is exhausted, I run command top and see that 0~1%
>> idle only,  ksoftirqd and kworker take most of my processor resource.
>>
>> Last week I discovered by chance that the module loaded in kernel can create
>> effects to performance of rate, in my case it is "iptables". If I unload all module
>> that related to iptables I can improve the performance.
>> So I wonder if I can do some thing with the Wi-fi driver to  improve rate?
>> Or the only solution is overclock/change my processor?

>Can you run 'perf top' on your system when it is under load so we can
>see where the CPU is being used the most?

I follow a tutorial to cross compile perf so here is my result


PerfTop:      70 irqs/sec  kernel:98.6%  exact:  0.0% [1000Hz cycles],  (all, 1 CPU)
-------------------------------------------------------------------------------

    39.43%  [kernel]       [k] csum_partial_copy_nocheck
     5.54%  [kernel]       [k] __kmalloc_track_caller
     4.93%  [kernel]       [k] kfree
     4.31%  [mac80211]     [k] ieee80211_tx_status
     4.31%  [kernel]       [k] memcpy
     3.49%  [kernel]       [k] __memzero
     3.29%  [kernel]       [k] mv_eth_poll
     3.29%  [kernel]       [k] __kfree_skb
     2.05%  [ath10k_pci]   [k] ath10k_ce_send_nolock
     1.44%  [mac80211]     [k] $a
     1.44%  [kernel]       [k] dev_gro_receive
     1.44%  [kernel]       [k] napi_gro_receive
     1.44%  [kernel]       [k] eth_type_trans
     1.44%  [kernel]       [k] inet_gro_receive
     1.44%  [kernel]       [k] skb_copy_and_csum_bits
     1.44%  [kernel]       [k] skb_segment
     1.44%  [ath10k_core]  [k] ath10k_htt_rx_amsdu_pop
     1.44%  [ath10k_core]  [k] ath10k_txrx_tx_unref
     1.23%  [kernel]       [k] local_bh_enable                                  
     1.23%  [kernel]       [k] kmem_cache_alloc                                 
     1.23%  [kernel]       [k] dev_hard_start_xmit 


Thank you in advance for your response,

NGUYEN Vu Hai
Acita-Sodielec
Route de Mayres - B.P. 9
12100 St GEORGES DE LUZENCON
FRANCE



Thanks,
Ben

>
> NGUYEN Vu Hai
> Acita-Sodielec
> Route de Mayres - B.P. 9
> 12100 St GEORGES DE LUZENCON
> FRANCE
>
>
>
>
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--
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com