In order to have deeper insights into the CPU load behavior, these experiments are performed using stress-ng tool in varying load conditions ranging from 10, 20, 30, 40, 50 and 100 %. This load variability is applied to 1 - 7 vCPUs on the only existing VM, which is provisioned with 2 vCPUs in this setup. Uptime and top commands are used for load collection from PM and VM in both CentOS and Ubuntu host.
To analyze the relationship between PM and VM, we present the scatter plots mapping load average of VM and PM. The following sections show the scatter plots.
5.3.1
Uptime tool
Figures 5.3, 5.4, 5.5 and 5.6 show the uptime load average values obtained from PM and VM in case of 1, 2, 3 and 7 vCPUs respectively. Their sub-figures (a) and (b) present the observations from CentOS and Ubuntu hosts respectively. In all the scatter plots, x-axis is the load average observed on guest and y-axis represents load average observed on host. The scatter plots of load ranging from 10, 20, 30, 50 and 100 % are are plotted. As an inital approach of analyzing results, a linear trendline as an overall interpolation and extrapolation referrence, in case of 100% load is drawn. This comes handy in showing the deviation of the scatter plots from linearity. However, the results of 4, 5 and 6 vCPUs are omitted due to similarity in most cases but their correlation co-efficient values are shown in section 5.4.
The following are the observations made based on these graphs.
• In all the cases - figures 5.3 to 5.6, scatter plots on Ubuntu host followed the linear trendline better than the CentOS scatter plots.
• The load behavior in the conditions below 100% load varies to a great extent, even though most of the plots observed positive correlation.
• The systems correlated in a proper trend with slight deviation at 100% load compared to the conditions under 100% load.
Chapter 5. Results and Analysis 39 Figure 5.3: Scatter plots showing the CPU load relationships between host and guest in varying load conditions - uptime tool.
(a) Correlation between CPU loads on host and guest - 1vCPU - CentOS device 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest CentOS Host, uptime, stress−ng on 1 vCPU
10% 20% 30% 40% 50% 100% linear
(b) Correlation between CPU loads on host and guest - 1vCPU - Ubuntu device 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest Ubuntu Host, uptime, stress−ng on 1 vCPU
10% 20% 30% 40% 50% 100% linear
However, the overall view shows that the plots do not completely obay the linear trendline. In some cases, it is slightly exponential too - figure 5.5 (a), 5.6 (b). It is anticipated that there is need for more experimentation and research in this regard. More iterations may be needed to make conclusions based on these observations. We can observe the top results from the 7vCPUs in the same scenario in the next section for comparison of the load behavior.
Chapter 5. Results and Analysis 40 Figure 5.4: Scatter plots showing the CPU load relationships between host and guest in varying load conditions - uptime tool.
(a) Correlation between CPU loads on host and guest - 2vCPU - CentOS device 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest CentOS Host, uptime, stress−ng on 2 vCPU
10% 20% 30% 40% 50% 100% linear
(b) Correlation between CPU loads on host and guest - 2vCPU - Ubuntu device 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest Ubuntu Host, uptime, stress−ng on 2 vCPU
10% 20% 30% 40% 50% 100% linear
5.3.2
Top tool
Figure 5.7 shows CPU load behavior as characterized by the tool “top”. Even though we have extracted top results in all the scenarios, we believe this one scenario would be sufficient for comparison and hence, omitted the other plots. The discussions section - 5.4, will present correlation co-efficient values from all
Chapter 5. Results and Analysis 41 Figure 5.5: Scatter plots showing the CPU load relationships between host and guest in varying load conditions - uptime tool.
(a) Correlation between CPU loads on host and guest - 3vCPU - CentOS device 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest CentOS Host, uptime, stress−ng on 3 vCPU
10% 20% 30% 40% 50% 100% linear
(b) Correlation between CPU loads on host and guest - 3vCPU - Ubuntu device 0 0.5 1 1.5 2 2.5 3 3.5 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest Ubuntu Host, uptime, stress−ng on 3 vCPU
10% 20% 30% 40% 50% 100% linear
the cases.
As we can interpret from figures 5.6 (a) and 5.7 (a), the load average observed by top tool differs from uptime tool to a major extent. However, the behavior shown in figures 5.6 (b) and 5.7 (b) on Ubuntu hosts highly coincides. From the above presented results and observations, we understand that CPU
Chapter 5. Results and Analysis 42 Figure 5.6: Scatter plots showing the CPU load relationships between host and guest in varying load conditions - uptime tool.
(a) Correlation between CPU loads on host and guest - 7vCPU - CentOS device 0 1 2 3 4 5 6 7 8 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest CentOS Host, uptime, stress−ng on 7 vCPU
10% 20% 30% 40% 50% 100% linear
(b) Correlation between CPU loads on host and guest - 7vCPU - Ubuntu device 0 1 2 3 4 5 6 7 8 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest Ubuntu Host, uptime, stress−ng on 7 vCPU
10% 20% 30% 40% 50% 100% linear
load relationships between host and guest show likeliness towards a linear rela- tionship in few cases, while few cases show the opposite. However, it can be seen that the gaps observed between the scatter plots are due to the interval between experimental runs.
Chapter 5. Results and Analysis 43 Figure 5.7: Scatter plots showing the CPU load relationships between host and guest in varying load conditions - top tool.
(a) Correlation between CPU loads on host and guest - 7vCPU - CentOS device 0 1 2 3 4 5 6 7 8 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest CentOS Host, top, stress−ng on 7 vCPU
10% 20% 30% 40% 50% 100%
(b) Correlation between CPU loads on host and guest - 7vCPU - Ubuntu device 0 1 2 3 4 5 6 7 8 0 0.5 1 1.5 2 2.5
Load Average on Guest
Load Average on Host
Correlation between CPU load of Host and Guest Ubuntu Host, top, stress−ng on 7 vCPU
10% 20% 30% 40% 50% 100%