netdev - RE: [PATCH net] net: ethernet: microchip: lan743x: Increase rx ring size to improve rx performance

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Date:   Fri, 29 Oct 2021 12:57:18 +0000
From:   <Yuiko.Oshino@...rochip.com>
To:     <andrew@...n.ch>
CC:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <Bryan.Whitehead@...rochip.com>, <UNGLinuxDriver@...rochip.com>
Subject: RE: [PATCH net] net: ethernet: microchip: lan743x: Increase rx ring
 size to improve rx performance

>-----Original Message-----
>From: Andrew Lunn <andrew@...n.ch>
>Sent: Thursday, October 28, 2021 12:03 PM
>To: Yuiko Oshino - C18177 <Yuiko.Oshino@...rochip.com>
>Cc: davem@...emloft.net; netdev@...r.kernel.org; Bryan Whitehead - C21958
><Bryan.Whitehead@...rochip.com>; UNGLinuxDriver
><UNGLinuxDriver@...rochip.com>
>Subject: Re: [PATCH net] net: ethernet: microchip: lan743x: Increase rx ring size
>to improve rx performance
>
>EXTERNAL EMAIL: Do not click links or open attachments unless you know the
>content is safe
>
>On Thu, Oct 28, 2021 at 11:03:15AM -0400, Yuiko Oshino wrote:
>> Increase the rx ring size (LAN743X_RX_RING_SIZE) to improve rx performance
>on some platforms.
>> Tested on x86 PC with EVB-LAN7430.
>> The iperf3.7 TCPIP improved from 881 Mbps to 922 Mbps, and UDP improved
>from 817 Mbps to 936 Mbps.
>>
>> Fixes: 23f0703c125b ("lan743x: Add main source files for new lan743x driver")
>> Signed-off-by: Yuiko Oshino <yuiko.oshino@...rochip.com>
>> ---
>>  drivers/net/ethernet/microchip/lan743x_main.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/microchip/lan743x_main.h
>b/drivers/net/ethernet/microchip/lan743x_main.h
>> index 34c22eea0124..aaf7aaeaba0c 100644
>> --- a/drivers/net/ethernet/microchip/lan743x_main.h
>> +++ b/drivers/net/ethernet/microchip/lan743x_main.h
>> @@ -831,7 +831,7 @@ struct lan743x_rx_buffer_info {
>>       unsigned int    buffer_length;
>>  };
>>
>> -#define LAN743X_RX_RING_SIZE        (65)
>
>65 is interesting. 2^N + 1. So there might be a reason for this?

The original developer wanted to give the hardware a power of 2 usable (which is the ring size -1) number of descriptors, but that is not required by the hardware so for this update we decided to take it back to "rounder" power of 2 memory request from the OS.
>
>> +#define LAN743X_RX_RING_SIZE        (128)
>
>129?
>
>        Andrew

Thank you!
Yuiko