public void OptimizeReorderVertexBuffer()

This function causes the vertices of the mesh to be reordered internally in an attempt to improve vertex cache utilisation on the graphics hardware and thus rendering performance. This operation can take a few seconds or more for complex meshes and should only be used where the ordering of the vertices is not significant as it will change - the order of the geometry itself is unaffected.

You should only use this function on meshes you generate procedurally in code, for regular mesh assets it is called automatically by the import pipeline when 'Optimize Mesh' is enabled in the mesh importer settings.

Additional Resources: Mesh.Optimize, Mesh.OptimizeIndexBuffers

using UnityEngine;public class Example : MonoBehaviour{    void Start()    {        Mesh mesh = gameObject.GetComponent<MeshFilter>().mesh;        mesh.OptimizeReorderVertexBuffer();    }}