JobifiedBaking

using System.Collections.Generic;
using Unity.Collections;
using Unity.Jobs;
using UnityEngine;
using System.Linq;
using Unity.Burst;

[BurstCompile]
public struct BakeJob : IJobParallelFor
{
    private NativeArray<int> meshIds;

    public BakeJob(NativeArray<int> meshIds)
    {
        this.meshIds = meshIds;
    }

    public void Execute(int index)
    {
        Physics.BakeMesh(meshIds[index], false);
    }
}

public static class JobifiedBaking
{
    const int meshesPerJob = 10;
    public static void BakeMeshes(Dictionary<MeshChunk,Mesh> meshes)
    {
        NativeArray<int> meshIds = new NativeArray<int>(meshes.Count, Allocator.TempJob);

        for (int i = 0; i < meshes.Keys.Count; ++i) {
            meshIds[i] = meshes[meshes.Keys.ElementAt(i)].GetInstanceID();
        }

        // This spreads the expensive operation over all cores.
        var job = new BakeJob(meshIds);
        job.Schedule(meshIds.Length, meshesPerJob).Complete();

        meshIds.Dispose();

        // Now instantiate colliders on the main thread.
        for (int i = 0; i < meshes.Keys.Count; i++) {
            meshes.Keys.ElementAt(i).meshCollider.sharedMesh = meshes[meshes.Keys.ElementAt(i)];
        }
    }
}