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

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Date:   Fri, 17 Nov 2023 18:16:02 +0000
From:   Simon Horman <horms@...nel.org>
To:     Vishvambar Panth S <vishvambarpanth.s@...rochip.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kuba@...nel.org, jacob.e.keller@...el.com,
        bryan.whitehead@...rochip.com, UNGLinuxDriver@...rochip.com,
        davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com
Subject: Re: [PATCH net-next] net: microchip: lan743x : bidirectional
 throughput improvement

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@...rochip.com>

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@...nel.org>

[1] https://lore.kernel.org/netdev/e5ffec56-5512-1acc-b85c-ac0771634c22@intel.com/