I am testing node with network load and I get the following profiling results:

 [Shared libraries]:
   ticks  total  nonlib   name
  285518   63.3%          /usr/bin/node
  21547    4.8%          /usr/lib/x86_64-linux-gnu/libc.so.6
    770    0.2%          [vdso]
    231    0.1%          /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.30
    114    0.0%          /usr/lib/x86_64-linux-gnu/libm.so.6

 [Summary]:
   ticks  total  nonlib   name
  44333    9.8%   31.0%  JavaScript
  43387    9.6%   30.3%  C++
  19641    4.4%   13.7%  GC
  308180   68.3%          Shared libraries
  55499   12.3%          Unaccounted

There is a high CPU load on the node itself, but what does this mean?
What is the bottleneck?