Performance Analysis for Improved RAM Utilization for Android Applications

Transcription

1 Performance Analysis for Improved RAM Utilization for Android Applications Deepali Kayande #1, Urmila Shrawankar #2 # Department of Computer Science & Engineering G. H. Raisoni College of Engineering, Nagpur, India 1 kayande.deepali@ieee.org, 2 urmila@ieee.org Abstract-- Memory management is a vital parameter in efficient working of any operating system. In the mobile devices, internal memory plays an important role in managing the running of process, services and applications which are either installed by the user or which are already present in the device. Thus this paper aims towards giving an approach for better utilization of the internal memory present in Android operating system for mobile phones. The memory architecture for the Android device has been studied and has been observed that the device comes loaded with many applications which require high RAM consumption for efficient working. Thus taking into consideration running of so many applications processes and services, it is important to efficiently use and manage the internal memory space present inside the mobile operating system. For this purpose, a dictionary based application called SMSLingo has been developed for compression of SMS texting. This application requires less memory space and less RAM consumption as compared to the default SMS messaging service provided by Android. Memory management of Android system has been compared with the one in Linux System. It has been observed that Mapped Memory, Anonymous Memory and Slab Memory is present in Android which is used for allotting temporary storage space for the data frequently used. Keywords: Linux Kernel, Dalvik Virtual Machine, Android Memory management, Android operating system, SMS text Compression, SMS language I. INTRODUCTION When mobile operating systems are considered, memory management plays the key role. As the mobile devices are constrained about the hardware part, special care has to be taken for the memory management. Android operating system is based on the Linux kernel which mainly has the paging system. The memory is categorised as internal memory, swap memory, external memory, etc. each having its own features and usage. The internal memory is used to store data like the text messages, multimedia messages, call logs, calendar activities, etc., unless and until the storage location is not changed and the by default settings are used. Efficient working of any operating system is based on its process management, device management and memory management. Out of these three issues, this paper talks about the memory management. As the name suggests, memory management helps in managing the system memory. The most important feature present in memory management is to enable dynamic allocation of portions of memory to the requesting processes. Memory management and memory optimization plays the most important role in any operating system, be it monolithic system or any mobile operating system. Various applications and approaches have been proposed in achieving the optimized use of memory in the operating system. This paper proposes one such application that aims at utilizing the internal memory of Android Mobile Operating System in an optimized fashion. Basic Android mobile phones support 150 MB of internal memory. Apart from the internal memory, mobile phones have an option of using the external memory which can be extended depending on the brand or type of the mobile phone handset. Thus the user can shift the desired applications from the internal memory to the external memory also. But basically the optimized and efficient use of the internal memory is a matter of concern. For the experimentation purpose, SMS application is being targeted, because by default all the SMS are stored inside the internal memory unless and until the storage location is not changed [2]. Thus the amount of memory saved after the optimization can be used for better functions [3]. Android device supports UTF-8 encoding of text characters in SMS application. Thus as compared to other mobile devices, Android consumes double amount of bytes while storing the SMS in inbox. Also, many Android devices do not support storing SMS in the external memory viz LG-C660. So, an application with less memory size and RAM requirement is developed in order to optimize the internal memory consumption during SMS texting is carried out on the device. The Experimental results are evaluated using 3 text compression techniques, Huffman Coding, RLE and SMS Lingo on few sample text data. Increase of 8-10% in compression ratio is achieved using the SMS Lingo compression algorithm in comparison with other available methods. Also this application is reasonably smaller in size as compared to the size of default SMS application present on Android platforms and smaller in comparison with the other SMS compressor

2 applications present for the platform. The RAM and cache memory consumption is around 3 MB for this application and the default Messaging application requires around 8 MB RAM size for its operation. Thus the proposed hybrid technique is reasonable with respect to RAM as well as cache memory consumption. II. LINUX KERNEL vs ANDROID OS Android OS is nearly similar to the Linux Kernel but not completely alike. It is directly derived from the Linux kernel that is why it is very much similar to it. Taking into consideration the mobile environment and the limitations of the system, Android OS has enhanced its features by adding more custom libraries to the already existing ones in order to support better system functionalities. For example, one enhancement is that Android devices are based on the Last-seen-first-killed design process. This process kills the least recently used process in order to make room for the new processes. Thus this process is similar to the Least-recently-used process present in Linux system. Also android come with task manager which helps in managing and killing of any unwanted applications, services or processes manually. Thus this feature helps in better utilization of RAM and the internal storage. A custom C Library is implemented in Android which is again derived from the standard C Library. This custom library is developed because it is finely suited for Android mobile platform having limited CPU and memory available. Even though Android is based on Java, JVM is not used in the android devices. Instead, Dalvik Virtual Machine is developed as the specific virtual machine for the android devices. DVM is specifically developed taking into consideration the memory constraints present in Android mobile devices. The conversion of.class file to.dex format is done by the system itself. Kernel is the central part of any operating system. It is an important part of the operating system which directly interrelates with the hardware. The specifications of the kernel depend upon the hardware on which it runs [10]. The basic facilities run by the kernel are Process Management, Memory Management, Device Management and System Calls [9]. Thus, Android also supports all these features. The brief description for these is as follows: A. Process management The execution of the applications is allowed by the kernel along with hiding of all the undesirable hardware details from the user. B. Memory Management It is the kernel responsibility to allow the processes running in the system access the memory as they require it. C. Device Management It is the kernel duty to enable the operating system to interact with the hardware peripherals. D. System Management This is the mechanism which is used by the application program to call a service from the system as and when needed. Fig 1: The Kernel Relation with Hardware and Applications III. ANDROID INTERNAL MEMORY A. Memory Architecture As computer operating system, memory in mobile operating system is also categorized as RAM, ROM and extended memory. Basic Android mobile phones have 256 MB RAM, 512 MB ROM and the external memory can be extended up to 32 GB with 600 MHz processor. Whereas, the basic android tablet supports 1 GB RAM and external memory can be extended up to 64 GB with 1 GHz processor. RAM supports swap memory, registers, paging system, etc. this memory is used to read and over write the data being used in mobile operating system. RAM is a temporary storage place for the operating system and the applications running on the device. Android, however, starts and stores many applications in the RAM which are not even used by the user. Thus, due to these unwanted applications, huge amount of RAM is consumed unnecessarily. This affects the system memory to run slow and requires manual turning off of such unwanted applications. Thus it becomes necessary to take care of proper utilization of RAM in order to prevent system from running on low memory. The concept was virtual memory is not present in Android OS and the cache memory can be erased manually but cannot be allotted by the user. The applications which

3 are stored in cache are decided by the system. But the cache memory engaged in various applications can be erased manually. ROM basically supports the start-up activities which are performed during the device are turned on. The start-up activities are vital and the data required for its functioning is non-volatile. Thus the important and nonerasable data is stored in ROM. Fig 2: The memory relationship interaction including drivers and memory management, while a set of APIs provides access to all of the underlying services, features, and hardware[12]. Linux kernel basically performs maximum work related to memory management inside the android operating system. Android supports page based memory management, typically the demand paging. Demand paging is a mechanism in which a page is brought into the working memory only when it is in demand, that is, only when it is needed. The advantages of supporting demand paging in mobile operating system is that, it requires lesser input output. Memory requirement in this mechanism is less. Also the response rate amongst the applications is faster. In demand paging, when a page is needed or demanded, it is referenced by the system. If the referenced page is invalid, the reference is aborted and a new reference is made. After referencing if the page is not found in memory, then it is brought into the memory for further functioning. B. Memory Management Android is a stack comprising of software meant for mobile devices which includes an operating system, middleware and applications. Android is a Linux based OS with 2.6.x kernel, which uses native open source C libraries. The Linux Kernel handles all the basic OS operations like device management, process management, memory management, and so on. The working of Android s process and memory management is uncommon. Android uses its own dedicated run time and virtual machine to manage application memory, similar to JAVA and.net. Android run time also manages the process lifetimes. This feature is missing in Java and.net frameworks [13]. Android confirms application receptiveness by stopping and killing processes as needed to free resources for higher-priority applications. Each Android application runs in a separate process within its own Dalvik instance and all the responsibility for memory and process management is charged over to the Android run time, which breaks and kills processes as needed to manage resources [6, 8]. Dalvik and the Android run time assemble on top of a Linux kernel that handles low-level hardware IV. MEMORY CONFIGURATION OF ANDROID DEVICE The Android operating system manages released applications which are working in the background. Thus it is the system responsibility to kill the applications when the system is in need of more memory. But, in this scenario Android system leaves too many applications and processes running in the background. This causes slackness in the system s performance. In order to avoid this inconvenience, advanced task managers are available in the Android system to improve the working of jobs. The task manager shows the details regarding the applications, processes and the services running in the background. Manually users can also delete any application, service or process if in case it is not needed. The memory configuration for Linux System and an Android device has been studied and the results are shown in the following tables. The memory configuration details of a Linux machine and for an Android Device LG-C660 are given in Table I. TABLE I Comparison for the Memory Configuration Details of Linux Machine and an Android Device Memory Details (kb) Entry Description Linux Android Machine Device MemTotal Total usable RAM MemFree Total free RAM memory Buffers Buffer cache memory Cached Memory in PageCache minus SwapCached SwapCached Memory in swapfile which is used as cache memory Active Memory that is active in use Inactive Memory that is free Active(anon) Anonymous memory that is active in use Inactive(anon) Anonymous memory that is free

4 Active(file) Memory related to file which is active Inactive(file) Memory related to file which is free Unevictable These are the pages that cannot be paged because the page might belong to a ramdisk Mlocked Memory consumed by the locked pages HighTotal Total memory which is not mapped into the kernel space Not Present HighFree Free memory which is not mapped into the kernel space 2496 Not Present LowTotal Total memory which is mapped into the kernel space Not Present LowFree Free memory which is mapped into the kernel space Not Present SwapTotal Total swap memory SwapFree Swap memory which is free Dirty Memory which is waiting and need to be written back on the disk Writeback memory which is active and is being written back on the disk 0 0 AnonPages Memory details regarding Anonymous memory Mapped Memory details regarding the mapped memory which allows communication among various files through a shared file. Shmem Memory occupied by the shared memory which is used in Inter Process Communication Slab Memory occupied by the in-kernel cache SReclaimable Memory which is a part of slab, and can be reclaimed SUnreclaim Memory which is a part of slab, and cannot be reclaimed KernelStack Memory occupied by the Stack Kernel PageTables Memory which is allotted to the lowest level of page tables NFS_Unstable NFS pages which are sent to the server but are not committed to stable storage. 0 0 Bounce Memory used by block device 0 0 WritebackTmp Memory used for temporary writeback buffers 0 0 CommitLimit Memory which is currently available to be allocated on the system Committed_AS Entry representing the worst case scenario in the device VmallocTotal Memory occupied by vmalloc VmallocUsed Memory used by vmalloc VmallocChunk Free memory of vmalloc HugePages_Total Total memory consumed by the huge pages 0 Not Present HugePages_Free Free memory of the huge pages which are not yet mapped 0 Not Present HugePages_Rsvd Memory reserved by the pages and not yet mapped 0 Not Present HugePages_Surp Surplus memory above the normal value of the huge pages 0 Not Present Hugepagesize Memory consumed by the huge page 4096 Not Present DirectMap4k Memory which is mapped using the page size 4k Not Present DirectMap4M Memory which is mapped using the page size 4M Not Present The table shows that High Memory and Low Memory are not present in the Android OS. High Memory is the memory which is referred by the kernel indirectly, if in case the userspace translation is not created in physical memory by the system. Whereas, Low Memory is the memory which has direct mapping present in the kernel. In Linux, multiple page sizes of the hardware can be accessed using the technique called Hugepages. This feature is absent in Android because the hardware present is limited in comparison with the Linux system hardware. The virtual memory statistics of a Linux machine and for an Android Device LG-C660 are given in Table II. The results in Table II below show that the concept of Swap Memory, Buffered Memory and Cache Memory is not present in Android OS whereas Mapped Memory, Anonymous Memory and Slab Memory are present in Android OS. The concept of Swap Memory has been replaced by Anonymous Memory in Android. Thus, when Anonymous Memory is requested by the system, reservation of this memory is made in place of Swap Memory and respective mapping is done to access the requested memory. Slab Memory is the concept which allots temporary space for the data which is allotted and freed again and again depending on the frequent use of the data. Linux kernel 2.6 is chosen as the base for Android OS because of its promising driver model, all the existing drivers, strong memory and process management, network support and all the other functionalities which are supported by an operating system. Android OS has added numerous libraries to enhance the working of the system [15]. The entries in Table I and Table II are derived after executing the memory related commands on Linux desktop and Android OS. These commands were run and tested in order to understand the similarities and the differences present in Linux and Android system which have nearly same, but not completely same kernel structure. Many similarities are observed in the results which are obtained. These similarities are present because Android is directly derived from the Linux kernel.

5 TABLE II Comparison of Virtual Memory Statistics of Linux Machine and an Android Device Platform Field Entry Description Linux Android Machine Device Procs r Processes waiting to enter run-time Yes Yes Uninterruptable b sleeping processes Yes Yes swpd Swap area in memory Yes No free Idle memory Yes Yes buff Buffered memory Yes No Memory cache Fast memory Yes No mapped Mapped memory No Yes anon Anonymous memory No Yes slab Contiguous memory No Yes Interrupts occurring in per second Yes Yes System Context switches cs occurring per second Yes Yes flt Page faults occurring No Yes us User time Yes Yes sy System time Yes Yes CPU id Idle time Yes Yes wa Wait time Yes Yes V. COMPARISON OF MEMORY CONFIGURATION OF SMSLINGO WITH OTHER APPLICATIONS Taking into consideration the high RAM consumption, limited CPU and memory availability, Android has become preferred platform for the developers for developing innovative applications. SMSLingo is one such application which aims towards less RAM consumption and better utilization of the internal memory in Android platform. The comparison of SMSLingo application with the default messaging service and other third party applications is shown in the above table. Parameters related to memory configuration are taken for comparison. Application size (.apk), data size and RAM requirement are the parameters which are tested. Among all the applications, SMSLingo has shown the most promising results. Thus taking into consideration the measly RAM behaviour in Android phones, SMSLingo application can be a promising replacement for the SMS texting application. Results obtained for memory optimization are better using SMSLingo because; the SMS is in readable format even after compressing thus the need for decompressing the SMS lessens after using SMSLingo application. Thus the internal memory required for storing the SMS is optimised promisingly using SMSLingo application. And the saved internal memory can be used for other better applications in return. TABLE III Comparison of Memory Statistics of SMSLingo application with the default Messaging service in an Android Device and also with few third party applications for SMS texting. Name SMSLingo Messaging PackSMS KyshMysh (developed Service (third party (third party SMS (provided SMS SMS compressor by compressor compressor application Android) application) application) Parameters for testing) Total memory 520 KB 420 KB 1.79 MB 88 KB Application size 512 KB (.apk) 392 KB 1.78 MB 76 KB Data size 12 KB 28 KB KB 12 KB RAM requirement (approx) 8.88 MB 15.5 MB 8.66 MB 3.49 MB Text Compression No Yes Yes Yes SMS readability (without decompression) No No No Yes Memory optimization No Yes Yes Yes TABLE IV Comparison of Compression Ratio achieved using Huffman, Run Length and SMSLingo Algorithm SMS Original Size (in Bytes) Compr -essed Size Huffman Run Length Hi, good morning! How are you doing? The meeting with principal has been postponed. It will be scheduled in next week most probably. The timing for the same will be conveyed later. Keep all your work ready so as to give your best. Take care. Bye! Hi! wish you many many happy returns of the day dear :) hope you have a wonderful birthday and a beauiful life ahead :) may God bless you today and forever. may all your wishes come true and you get all the success you deserve. hope to meet you in evening if you manage to steal some time for us. let us know the time and venue for party. have a nice day dear! take care :)

6 Compr -ession Ratio SMSLingo Huffman Run Length 44.76% 47.14% 71.84% 73.42% SMSLingo 82.92% 83.64% Table IV is showing a comparison between Huffman, Run Length and SMSLingo algorithm. Among these three, SMSLingo is showing the most promising results with approximately 10% rise in the compression ratio. Thus, using this hybrid compression technique for text compression helps in optimising the space required per text file while storing in the internal memory. VI. CONCLUSION Android device supports UTF-8 encoding for the text in SMS. This encoding consumes double number of bytes as compared to the regular character encoding which is supported by rest of the mobile operating systems. Thus the space required in storing the SMS in internal memory is doubled and thus it reduces the space which can rather be used for other applications. Thus SMSLingo helps in optimizing the internal storage usage and RAM consumption on the Android device. The experimental results have shown that the RAM consumption of SMSLingo is least in comparison with the default messaging service present in Android and the other third party applications for SMS services. Apart from promising results in RAM consumption, SMSLingo is also better in the compression ratio achieved after processing the text files. Thus the amount of internal memory saved after compressing and saving the text files using SMSLingo is better as compared to the other text file compressor applications available for Android. This application can be extended for large text files and thus better optimization can be achieved for the storage space required for these files. The space preserved in the internal memory after using the compression technique, can be used for the storage of other applications. 5. S.R. Kodituwakku and U. S.Amarasinghe, Comparison Of Lossless Data Compression Algorithms For Text Data, Indian Journal of Computer Science and Engineering, Vol 1 No 4, Shane Conder and Lauren Darcey, Android Wireless Application Development, Pearson Education, Inc, Liu Pu, Performance Analysis of Short Message Service, International Symposium on Intelligent Ubiquitous Computing and Education, Reto Meire, Professional Android 2Application Developmen, Wiley Publishing, Inc, Daniel P. Bovet, Marco Cesati, Understanding the Linux Kernel, 3 rd Edition, O Reilly Publications, Mel Gorman, Understanding the Linux Virtual Memory Manager, Pearson Education, Java Virtual Machine [online], available Memory Management in Android [online], available David Ehringer, The Dalvik Virtual Machine Architecture, [online], available Machine.pdf 14. A Brief Overview of Dalvik Virtual Machine [online], available, Frank Make1 and Yu-Hsuan Chan, A Survey on Android vs. Linux. REFERENCES 1. Ningde Xie, et al., Using Lossless Data Compression in Data Storage Systems, IEEE Transactions on Computers, Vol. 60, No. 3, March Ahmad Affandi, et al., The Application of Text Compression to Short Message Service Using Huffman Table, Jurnal Generic, Indonesia, Stefan Böttcher, et al., Search and Modification in Compressed Texts, Data Compression Conference, Zigurd Mednieks, et al., Programming Android, O Reilly Publications, 2011