> On 15.07.2021., at 18:53, jerome.bay...@student.uliege.be wrote: > > Dear vpp-dev, > > I'm trying to do some IPv6 in IPv6 encapsulation with no tunnel configuration. > > The objective is to encapsulate the received packet in an other IPv6 packet > that will also "contain" a Hop-by-hop extension header. In summary, the > structure of the final packet will look like this : Outer-IP6-Header -> > Hop-by-hop-extension-header -> Original packet. > > The main concern here is that the size of the outer IP6 header + the size of > the extension header > 128 bytes sometimes. When it arrives, I cannot write > my data inside the buffer pre-data area because it has a size of 128 bytes. I > already asked for solutions previously and I was adviced to either increase > the size of the pre-data area by recompiling VPP or create a new buffer for > my data and then chain it to the original one. I was able to create a buffer > chain that seemed to work perfectly fine. > > However, when I tried to perform some performance tests I was quite > disappointed by the results : the buffer allocation for each packet is not > efficient at all. My question is then : Is there any way to increase the > performances ? To allocate buffers, I use the function "vlib_buffer_alloc" > defined in "buffer_funcs.h" but is it the right function to use ?
I’m quite sure vlib_buffer_alloc() can allocate buffers very fast. hopefully you are not calling that function for one buffer at a time... > > In my case, the best option would be to have more space available in the > buffer's pre-data area but VPP does not seem to be built in a way that allows > easy modifications of the "PRE_DATA_SIZE" value. Am I right or is there any > "clean" method to change this value ? PRE_DATA_SIZE is compile time constant for a good reason. making it configurable will decrease performance of almost every dataplane component. — Damjan
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