Very slow visualization of a huge point cloud inside RViz

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Hi, I am trying to visualize a huge point cloud inside RViz. I noticed that the visualization is very slow (less than 1 FPS as shown in the bottom right side RViz). Please see below a table showing the FPS and other details-

|-----------------|-----|-----------|--------------|
| Publishing Freq | FPS | CPU Usage | Memory Usage |
|-----------------|-----|-----------|--------------|
|      10 Hz      |  0  |    4%     |     30%      |
|-----------------|-----|-----------|--------------|
|       5 Hz      |  0  |    4%     |     28%      |
|-----------------|-----|-----------|--------------|
|       None      |  0  |    4%     |     25%      |
|-----------------|-----|-----------|--------------|

Below are the details of the environment-

• Intel® Xeon(R) CPU E5-2640 v2 @ 2.00GHz × 17
• GeForce GTX 1050 Ti/PCIe/SSE2
• 32 GB Memory
• Ubuntu 14.04 LTS 64 Bit OS

During the experiment, nvidia-smi shows less than 20% GPU usage. Below is the minimal code to reproduce the issue-

#include <ros/ros.h>
#include <sensor_msgs/PointCloud2.h>
#include <pcl_conversions/pcl_conversions.h>
#include <pcl/point_cloud.h>
#include <pcl/point_types.h>
#include <pcl/conversions.h>

int main(int argc, char** argv)
{
    ros::init(argc, argv, "pcl_tutorial");
    ros::NodeHandle nh;
    ros::Publisher pub_output = nh.advertise<sensor_msgs::PointCloud2>("points", 1);

    // number of points in point cloud
    int n = 8000000;

    // create a point cloud with random data
    pcl::PointCloud<pcl::PointXYZRGB> cloud;
    cloud.width = n;
    cloud.height = 1;
    cloud.is_dense = false;
    cloud.points.resize(cloud.width * cloud.height);

    for (size_t i = 0; i < cloud.points.size(); ++i) {
        cloud.points[i].x = 1024 * rand() / (RAND_MAX + 1.0f);
        cloud.points[i].y = 1024 * rand() / (RAND_MAX + 1.0f);
        cloud.points[i].z = 1024 * rand() / (RAND_MAX + 1.0f);
        cloud.points[i].r = 255.0 * rand();
        cloud.points[i].g = 255.0 * rand();
        cloud.points[i].b = 255.0 * rand();
    }

    // convert to PointCloud2
    sensor_msgs::PointCloud2 temp_cloud;
    pcl::toROSMsg(cloud, temp_cloud);
    // attach a frame
    temp_cloud.header.frame_id = "base";

    boost::shared_ptr<sensor_msgs::PointCloud2> cloud2 = boost::make_shared<sensor_msgs::PointCloud2>(temp_cloud);

    ros::Rate loop_rate(5);
    while (ros::ok()) {
        // update the timestamp
        cloud2->header.stamp = ros::Time::now();
        pub_output.publish(cloud2);

        ros::spinOnce();
        loop_rate.sleep();
    }
    return 0;
}

Following command was used for calculating CPU Usage-

grep 'cpu ' /proc/stat | awk '{usage=($2+$4)*100/($2+$4+$5)} END {print usage "%"}'

Memory Used-

free | grep Mem | awk '{print $3/$2 * 100.0}'

Following are my questions-

1. How to know the FPS of the followings-
   • Point cloud publisher and receiver?
   • Point cloud visualization inside RViz?
2. Why RViz is showing so slow visualization?
3. How to increase the FPS of visualization inside RViz?