And to answer biffer question, buffer memory is allocated by vpp.

— 
Damjan

> On Feb 1, 2019, at 3:51 PM, Dave Barach via Lists.Fd.Io 
> <dbarach=cisco....@lists.fd.io> wrote:
> 
> Next frames are the physical manifestations of graph arcs. Pending frames are 
> graph scheduler run-queue entries. 
> 
> -----Original Message-----
> From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Raj
> Sent: Friday, February 1, 2019 9:47 AM
> To: vpp-dev <vpp-dev@lists.fd.io>
> Subject: Re: [vpp-dev] Understanding vlib_frame_t
> 
> Thanks Damjan and Dave. These small explanations will greatly help in making 
> sure what I understand from reading code is correct.
> 
> Just a couple of followup questions, I hope these will help those reading the 
> archives later too in understanding the nuances of VPP architecture.
> 
> vlib_get_buffer() translates the buffer index into buffer pointer.
> Where exactly is the buffer memory getting allocated, when packets are coming 
> in via dpdk-input? Is this allocation is done by DPDK or this is done by VPP. 
> If I understand correctly vlib_buffer_t is pointing to this location.
> 
> Also as I understand, a graph nodes gets a vector. This vector is a frame 
> which holds a set of 4 Byte buffer indices which points to the the actual 
> buffer, containing packets. Node process all these packets (max 256) and 
> transmit to the next node. While reading code in this area, after processing 
> this there is reference to next frame and pending frame. I could not figure 
> out what these are and for what they are being used.
> 
> Thanks and Regards,
> 
> Raj
> 
>> On Thu, Jan 31, 2019 at 9:31 PM Dave Barach (dbarach) <dbar...@cisco.com> 
>> wrote:
>> 
>> In vlib – vpp’s basic vector library - frames comprise a single vector, a 
>> set of scalar variables, and some flags.
>> 
>> 
>> 
>> At node creation time, each graph node registration indicates the size of a 
>> vector element, and the total size of scalar data. Vlib_frame_t vectors 
>> include up to VLIB_FRAME_SIZE (256) vector elements of the indicated size.
>> 
>> 
>> 
>> In the vpp/vnet use case, vector elements are 32-bit buffer handles, easily 
>> converted to vlib_buffer_t pointers. Most graph nodes do not use scalar data.
>> 
>> 
>> 
>> An sample use case for per-frame scalar data: send all these packets in the 
>> vector to a certain ip address, where the ip address could be stored in 4 or 
>> 16 octets’ worth of scalar data.
>> 
>> 
>> 
>> HTH... Dave
>> 
>> 
>> 
>> -----Original Message-----
>> From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Raj
>> Sent: Thursday, January 31, 2019 9:27 AM
>> To: vpp-dev <vpp-dev@lists.fd.io>
>> Subject: [vpp-dev] Understanding vlib_frame_t
>> 
>> 
>> 
>> Hello all,
>> 
>> 
>> 
>> Continuing my reading of VPP code, I have a query regarding packet handling.
>> 
>> 
>> 
>> When a node gets a vector of packets to process, if I understand correctly, 
>> this would be a vlib_frame_t instance. From this vlib_frame_t instance 
>> arguments[0] is the offset to first  packet, arguments[1] is the offset to 
>> second  packet and so on, upto xx number of packets. Is this understanding 
>> correct? if yes, how much is the maximum size of the packet buffer?
>> 
>> 
>> 
>> Also what is the significance of scalar_size/vector_size in vlib_frame_t? 
>> Does it mean the number of frames/size of frames?
>> 
>> 
>> 
>> in vlib/main.c there is a statement  vec_resize (nm->pending_frames, 32). In 
>> here, what is pending_frames and what is the significance of number 32?
>> 
>> 
>> 
>> I know I have been asking too many questions over here and very grateful to 
>> all who answer.
>> 
>> 
>> 
>> Thanks a lot!
>> 
>> 
>> 
>> Raj
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