Power Measurements using performance counters

Transcription

1 Power Measurements using performance counters CSL862: Low-Power Computing By Suman A M (2015SIY7524)

2 Android Power Consumption in Android Power Consumption in Smartphones are powered from batteries which are limited in size and therefore capacity. Therefore Power management in Smartphone is of great concern. Objective: The Objective was to monitor the Power, performance and Frequency of CPU and GPU on running various benchmarks to gather data. Platform Specifications Phone Model : Mi4i Processor : Qualcomm MSM8939 GPU : Qualcomm Adreno 405 System RAM : 2GB CPU Cores : 8x Arm cortex A53 OS : Android 5.0 Figure 1: Test Platform Mi4i Smartphone Tools used: Bench mark Apps: Benchmark apps are standard application programs used to stress various resources of a system. SPEC CPU: SPEC CPU is industry-standardized, CPU-intensive benchmark suite, stressing a system's processor, memory subsystem and compiler. It contains 12 different benchmark tests. It provides a comparative measure of compute-intensive performance across the widest practical range of hardware using workloads developed from real user applications. Performance test Mobile: Performance test Mobile is an Android Application used to benchmark an Android device using a variety of different speed tests and compare the results to other device. It consists of various Benchmarking tests.

3 Power (W) Experiment: Setup: The Setup includes an app HWMonitor pro which can provide with the following data (as in fig ) at a time interval of 0.5 Second which is acquired in PC through Remote IP interface provided by the app. The data can be logged in CSV format which is imported to MS Excel for analysis and Charts The Experiment is conducted by running HWMonitor pro app in background which collects the performance and power data and transmits it to remote PC through IP. The power is measured by monitoring the drain current from the battery given by hardware measuring circuits present in the smartphone. Initially the systems Idle power is measured with the phone in screen off mode where all the CPUs are in sleep state. When the phone wakes the LCD is on and the LCB power is recorded which forms the base power of the smartphone. and the benchmark app is run in sequence one by one with an interval of 2 seconds between two benchmarks Spec CPU: SPEC CPU is industry-standardized, CPU-intensive benchmark suite, stressing a system's processor, memory subsystem and compiler. It contains 12 different benchmark tests. It provides a comparative measure of compute-intensive performance across the widest practical range of hardware using workloads developed from real user applications. The Spec CPU Benchmarks is executed in Smartphone using an Android apk. The results of the experiment shows that all these benchmarks consume same power around 2.5 to 3W as these are assigned to single core by the scheduler and there is no control to allocate more cores to the process and thus all should similar power values SPEC CPU Data MCF vortex bzip2 crafty gcc Benchmarks Figure 2: Power values of SPEC CPU Benchmarks

4 Pass Mark Benchmark: The Passmark softwares provides a set of standard tests for benchmarking the performance of an Android smartphone Benchmarks: CPU Tests Integer Math Operations The test uses a large set of random 32-bit and 64-bit integers and adds, subtracts, multiplies and divides these numbers. Floating Point Math Operations Similar to Integer test it perform same operations with Floating point data Prime Number Test - This algorithm uses loops and CPU operations that are common in computer software, and determines the speed at which numbers can be compared with other numbers String Sorting Test - The String Sorting Test uses the qsort algorithm to see how fast the CPU can sort strings Data Encryption Test - The Encryption Test encrypts blocks of random data using the Blowfish algorithm, This test uses many of the techniques in the math tests, but also uses a large amount of binary data manipulation and CPU mathematical functions like 'to the power of'. Data Compression Test - The compression test uses an Adaptive encoding algorithm based on a method described by from Ian H. Witten, Radford M. Neal, and John G. Cleary in an article called "Arithmetic Coding for Data Compression". The system uses a model which maintains the probability of each symbol being the next encoded Memory Tests Memory Read Test and Memory Write Test - A Memory File is created in RAM. The size of the Memory File is determined by the amount of ram currently available. GPU Stress Test Three helicopters travel around the scene featuring 150 trees on a terrain with water. The terrain is formed with 5,000 triangular polygons (15,000 vertices). The trees and water consist of 2 polygons (6 vertices) and each helicopter object consists of 1,120 triangular polygons (3,360 vertices). Lighting & alpha blending are enabled. Following Parameters are recorded for analysis: CPU Frequency (Core 0, Core 4) CPU Utilization GPU Frequency Power

5 Figure 3: Performance chart of benchmarks The Power Consumption of the various benchmarks is plotted in fig 3. The data consists of the Minimum, Maximum and the Average Power consumed by each benchmark. From the experiment following observations are made for each benchmark. Figure 4: Power vs CPU Utilisation graph Idle: The Idle power for the smartphone is very low 0.18W when it is in sleep it disable all the processing modes and uses only essential resources like GSM and 3G connectivity resources. The power consumption is there only when there is a data transaction with the network.

6 LCD: LCD is the most power consuming part of the Smartphone since it consumes a constant power independent of the applications load it always remain powered. It consumed 0.8 W of continuous power until there is an operation being performed in Phone. Math Operations (Fixed point): The Math operations run a set of Math operations and compute the results. It is highly CPU Intensive process and the CPU Utilisation is seen to be 98% also the power consumed is 6.7 W which is mainly consumed by the CPU. Math Operations (Floating point): The Floating Point operations consumed 4.7 W which is less than Math Operations which can be related to reduction in CPU usage (85 %) mainly due to floating point operations being performed by FPU unit and thus consuming less power. Prime Number : Prime Number detection as it many loops and memory operations the CPU is not fully utilised thus is consuming a power of 5.7 W. String Sorting: String sorting uses Quick sort algorithm which utilizes the CPU to the maximum as the sorting is not limited anywhere by memory operations and it CPU is utilised to its full strength to compute the results and thus has highest power of 7.5 W. Data Encryption : It also similar to Prime number detection the CPU Utilisation is low as data encryption has memory dependence. It consumed 6.4 W which less that String sorting. Figure 5: CPU Utilisation for various Benchmarks

7 POWER DRAIN FROM BATTERY (W) Power (W) Power (W) Power (W) Figure 6: Average, Min and Max Power consumption for various Benchmarks Memory Read and Write: Memory operations perform a transfer a block file from or to RAM. The CPU Utilisation is very low (~14%) as it is purely a memory bound operation. Thus Power consumption of 2.1 W ( ) W can be inferred to be consumed by the Memory controller only. It is visible from graph that write cycles are consuming more power than read cycle as Memory write is a power intensive operation. GPU Test: The GPU test stressed the GPU operations with its 3d vector processing operations. It consumed 3.3 W of Power and the CPU utilisation is very low (11%) showing that the power is being utilised mainly by the GPU. It also seen from fig. 7 that GPU frequency has increased to 550MHz from 400 MHz operated in all other operations.

8 Figure 7: GPU Frequency for various Benchmarks Conclusion: The Power distribution for various benchmark apps were analysed and from inference we can relate that operations that utilise CPU consume the most power peak of 7.5 W in String operation. Therefore CPU has the highest power rating based on operating frequency. The LCD consumes a continuous power of 0.8 W which is throughout the use of a smart phone compared to CPU which are burst of peak power based on operations. The GPU and Memory controllers consume considerably less power compared to CPU and contribute less to the power consumption of the system.