Hi,
Recently I’m developing a plugin based on VPP 18.07 to decode specified
packets. I added it between dpdk-input and interface-output using the same
method of adding sample plugin in VPP source code. To test its performance in
theory , I used clib_cpu_time_now() to calculate the average cpu time cost
when packets go through my pulgin.When I use differnet tx speed to send
packets to the device using VPP and my plugin , it turns out that the average
cpu time changes as the tx speed changes. At frist , I assume it is caused by
the cpu time cost when VPP moves packets to the next node. So I calculate the
average cpu time of each node but it appears the same.Then, I use the sample
plugin to operate the same test. The result is similar although it does not
fluctuate much.
Now I’m confused. Isn’t it that all packets go through the same code and cost
the same cpu time ?
Here is my code and test result.
Code added in sample/node.c:
static uword
sample_node_fn (vlib_main_t * vm,
vlib_node_runtime_t * node,
vlib_frame_t * frame)
{
from = vlib_frame_vector_args (frame);
n_left_from = frame->n_vectors;
next_index = node->cached_next_index;
sample_main.last_cpu_time = clib_cpu_time_now ();
sample_main.total_pkts += n_left_from;
………
while (n_left_from > 0){
………
}
………
vlib_node_increment_counter (vm, sample_node.index,
SAMPLE_ERROR_SWAPPED, pkts_swapped);
sample_main.total_cpu_time += clib_cpu_time_now() - sample_main.last_cpu_time;
return frame->n_vectors;
}
Test result:
Tx speed(Mb/s) Average cpu time
190 14
475 12
665 9
950 7
1140 7
1900 6
2895 6
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