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. 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. Andrew
