Re: [PATCH net-next] net: microchip: lan743x : bidirectional throughput improvement

[Jacob Keller]

On 11/17/2023 10:16 AM, Simon Horman wrote:
> On Thu, Nov 16, 2023 at 11:13:50AM +0530, Vishvambar Panth S wrote:
>> The LAN743x/PCI11xxx DMA descriptors are always 4 dwords long, but the
>> device supports placing the descriptors in memory back to back or
>> reserving space in between them using its DMA_DESCRIPTOR_SPACE (DSPACE)
>> configurable hardware setting. Currently DSPACE is unnecessarily set to
>> match the host's L1 cache line size, resulting in space reserved in
>> between descriptors in most platforms and causing a suboptimal behavior
>> (single PCIe Mem transaction per descriptor). By changing the setting
>> to DSPACE=16 many descriptors can be packed in a single PCIe Mem
>> transaction resulting in a massive performance improvement in
>> bidirectional tests without any negative effects.
>> Tested and verified improvements on x64 PC and several ARM platforms
>> (typical data below)
>>
>> Test setup 1: x64 PC with LAN7430 ---> x64 PC
>>
>> iperf3 UDP bidirectional with DSPACE set to L1 CACHE Size:
>> - - - - - - - - - - - - - - - - - - - - - - - - -
>> [ ID][Role] Interval           Transfer     Bitrate
>> [  5][TX-C]   0.00-10.00  sec   170 MBytes   143 Mbits/sec  sender
>> [  5][TX-C]   0.00-10.04  sec   169 MBytes   141 Mbits/sec  receiver
>> [  7][RX-C]   0.00-10.00  sec  1.02 GBytes   876 Mbits/sec  sender
>> [  7][RX-C]   0.00-10.04  sec  1.02 GBytes   870 Mbits/sec  receiver
>>
>> iperf3 UDP bidirectional with DSPACE set to 16 Bytes
>> - - - - - - - - - - - - - - - - - - - - - - - - -
>> [ ID][Role] Interval           Transfer     Bitrate
>> [  5][TX-C]   0.00-10.00  sec  1.11 GBytes   956 Mbits/sec  sender
>> [  5][TX-C]   0.00-10.04  sec  1.11 GBytes   951 Mbits/sec  receiver
>> [  7][RX-C]   0.00-10.00  sec  1.10 GBytes   948 Mbits/sec  sender
>> [  7][RX-C]   0.00-10.04  sec  1.10 GBytes   942 Mbits/sec  receiver
>>
>> Test setup 2 : RK3399 with LAN7430 ---> x64 PC
>>
>> RK3399 Spec:
>> The SOM-RK3399 is ARM module designed and developed by FriendlyElec.
>> Cores: 64-bit Dual Core Cortex-A72 + Quad Core Cortex-A53
>> Frequency: Cortex-A72(up to 2.0GHz), Cortex-A53(up to 1.5GHz)
>> PCIe: PCIe x4, compatible with PCIe 2.1, Dual operation mode
>>
>> iperf3 UDP bidirectional with DSPACE set to L1 CACHE Size:
>> - - - - - - - - - - - - - - - - - - - - - - - - -
>> [ ID][Role] Interval           Transfer     Bitrate
>> [  5][TX-C]   0.00-10.00  sec   534 MBytes   448 Mbits/sec  sender
>> [  5][TX-C]   0.00-10.05  sec   534 MBytes   446 Mbits/sec  receiver
>> [  7][RX-C]   0.00-10.00  sec  1.12 GBytes   961 Mbits/sec  sender
>> [  7][RX-C]   0.00-10.05  sec  1.11 GBytes   946 Mbits/sec  receiver
>>
>> iperf3 UDP bidirectional with DSPACE set to 16 Bytes
>> - - - - - - - - - - - - - - - - - - - - - - - - -
>> [ ID][Role] Interval           Transfer     Bitrate
>> [  5][TX-C]   0.00-10.00  sec   966 MBytes   810 Mbits/sec   sender
>> [  5][TX-C]   0.00-10.04  sec   965 MBytes   806 Mbits/sec   receiver
>> [  7][RX-C]   0.00-10.00  sec  1.11 GBytes   956 Mbits/sec   sender
>> [  7][RX-C]   0.00-10.04  sec  1.07 GBytes   919 Mbits/sec   receiver
>>
>> Signed-off-by: Vishvambar Panth S <vishvambarpanth.s@xxxxxxxxxxxxx>
> 
> Thanks,
> 
> I think you should have included Jacob's Reviewed-by tag from
> the previous posting of this patch [1].
> 
> And echoing his comments there, a very nice performance boost :)
> 
> Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
> 
> [1] https://lore.kernel.org/netdev/e5ffec56-5512-1acc-b85c-ac0771634c22@xxxxxxxxx/

For the record, this version also looks good to me!

Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>