Hi Andrew, On 19/03/24 6:49 pm, Andrew Lunn wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > On Tue, Mar 19, 2024 at 12:54:30PM +0000, Parthiban.Veerasooran@xxxxxxxxxxxxx wrote: >> Hi Andrew, >> >> On 07/03/24 10:38 pm, Andrew Lunn wrote: >>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe >>> >>>> @@ -55,6 +77,14 @@ >>>> (OA_TC6_CTRL_MAX_REGISTERS *\ >>>> OA_TC6_CTRL_REG_VALUE_SIZE) +\ >>>> OA_TC6_CTRL_IGNORED_SIZE) >>>> +#define OA_TC6_CHUNK_PAYLOAD_SIZE 64 >>>> +#define OA_TC6_DATA_HEADER_SIZE 4 >>>> +#define OA_TC6_CHUNK_SIZE (OA_TC6_DATA_HEADER_SIZE +\ >>>> + OA_TC6_CHUNK_PAYLOAD_SIZE) >>>> +#define OA_TC6_TX_SKB_QUEUE_SIZE 100 >>> >>> So you keep up to 100 packets in a queue. If use assume typical MTU >>> size packets, that is 1,238,400 bits. At 10Mbps, that is 120ms of >>> traffic. That is quite a lot of latency when a high priority packet is >>> added to the tail of the queue and needs to wait for all the other >>> packets to be sent first. >>> >>> Chunks are 64 bytes. So in practice, you only ever need two >>> packets. You need to be able to fill a chunk with the final part of >>> one packet, and the beginning of the next. So i would try using a much >>> smaller queue size. That will allow Linux queue disciplines to give >>> you the high priority packets first which you send with low latency. >> Thanks for the detailed explanation. If I understand you correctly, >> >> 1. The tx skb queue size (OA_TC6_TX_SKB_QUEUE_SIZE) should be 2 to avoid >> the latency when a high priority packet added. >> >> 2. Need to implement the handling part of the below case, >> In case if one packet ends in a chunk and that chunk still having some >> space left to accommodate some bytes from the next packet if available >> from network layer. > > This second part is clearly an optimisation. If you have lots of full > MTU packets, 1514 bytes, they take around 24 chunks. Having the last > chunk only 1/2 full does not waste too much bandwidth. But if you are > carrying lots of small packets, say voice, 130 bytes, the wasted > bandwidth starts to add up. But is there a use case for 10Mbps of > small packets? I doubt it. Yes, for sure there is a possibility to get into this scenario and the protocol also supports that. But as proposed by you below, let's implement it as part of optimization later. > > So if you don't have the ability to combine two packets into one > chunk, i would do that later. Lets get the basics merged first, it can > be optimised later. Yes, I agree with this proposal to get the basic version merged first. Best regards, Parthiban V > > Andrew
