  Particle production at LHC energies involves the interplay of hard
(perturbative) and soft (non-perturbative) QCD processes. Global observables,
such as the charged-particle multiplicity, are related to the initial geometry
and the energy density produced in the collision. They are important to
characterise relativistic heavy-ion collisions and to constrain model
calculations. The LHC produced Xenon-Xenon collisions for the first time in
October 2017. New results on the primary charged-particle pseudorapidity
density, and its pseudorapidity and centrality dependence are presented for
this lighter and deformed nucleus, and compared to measurements obtained for
lead ions. New results will also be presented for p-Pb collisions at the
highest energy of 8.16 TeV, as part of an overview of all the measurements at
LHC Run 1 and 2 energies. These studies allow us to investigate the evolution
of particle production with energy and system size and to compare models based
on various particle production mechanisms and different initial conditions.
