Kernel Architecture Process Management Memory Management File Systems Potpourri
Q. What type of Kernel does Windows Mobile have?
Q. Hybrid kernel. This is a kernel structure similar to a microkernel, but implemented as a monolithic kernel. All (or nearly all) services are in kernel space. There is no performance overhead associated with microkernel message passing and context switching between kernel and user mode. There are none of the benefits of having services in user space.
Q. What is the size of the kernel address space?
A. 32 MB In CE 6.0 (version the new windows mobile will be based on) this process address space is increased to 1 GB.
Q. What is the maximum number of processes that can be run?
A. 32 Processes CE 6.0 now allow for up to 32,768 processes running at one time.
Q. How much virtual address space can each process run in?
A. 32MB There is 2GB of virtual address space for the kernel with each of the processes running in a 32MB slot. In CE 6.0 each process gets a 2GB virtual address space to run in.
Q. Windows Mobile 6 is based on which other Windows OS family and version? CE 5.2.
A. Windows Mobile is best described as a subset of platforms based on a Windows CE underpinning. Specifically it is based on the CE version 5.2 kernel/architecture.
Q. What are the 5 running states of a thread.
A. Running, suspended, sleeping, blocked, or terminated
Q. T/F. Windows CE uses a priority-based time-slice algorithm to schedule the execution of threads.
A. True Because Windows CE does not have priority classes, the process in which the thread runs does not influence thread priorities. All the priorities can be used in the same process. THREAD_PRIORITY_TIME_CRITICAL THREAD_PRIORITY_HIGHEST THREAD_PRIORITY_ABOVE_NORMAL THREAD_PRIORITY_NORMAL THREAD_PRIORITY_BELOW_NORMAL THREAD_PRIORITY_LOWEST THREAD_PRIORITY_ABOVE_IDLE THREAD_PRIORITY_IDLE
Q. Threads with the same priority run with which type of scheduling (ie. FCFS, Round Robin, SPN, SRT, HRRN)?
A. Round Robin Threads with a higher priority are scheduled to run first. Threads with the same priority run in a round- robin fashion—when a thread has stopped running, all other threads of the same priority run before the original thread can continue. Threads at a lower priority do not run until all threads with a higher priority have finished, that is, until they either yield or are blocked. If one thread is running and a thread of higher priority is unblocked, the lower-priority thread is immediately suspended and the higher-priority thread is scheduled.
Q. Threads generally run for a time slice (or quantum). Generally how long is one time slice?
A. 25 milliseconds. After that time, if the thread has not relinquished its time slice and is not time-critical, it is suspended, and another thread is scheduled to run. Threads at the highest priority level—THREAD_PRIORITY_TIME_CRITICAL—continue executing without interruption until they have finished, unless interrupted by an Interrupt Service Routine (ISR). Thread priorities are fixed and do not change. Windows CE does not age priorities, boost foreground thread priorities, or mask interrupts based on these priority levels. The kernel can temporarily modify thread priorities when a low-priority thread is using a resource that delays the execution of a high-priority thread wanting to use the same resource. Windows CE boosts the priority of the low-priority thread until it releases the resource required by the higher priority thread. This scenario is called priority inheritance, and is designed to prevent a low-level thread running before higher level threads, a problem known as priority inversion. Windows CE will go through the entire chain of threads trying to correct a priority inversion problem. A thread can also be suspended for a variable time, according to the programmer.
Q. Define Slot Implementation in relation to Windows Mobile 6.0
A. A process is run based on this (slot) implimentation.
Q. T/F Windows CE 5.2 Core exclusively utilizes a virtual memory management system in an attempt to increase efficient use of system resources.
A. False – it also uses real memory.
Q. T/F Windows CE 5.2 Core implements many significant changes in its memory management system as compared to previous versions of Windows CE Core.
A. False – All changes to the memory management system in Windows CE have been minor since version 1.0.
Q. T/F Windows CE 5.2 Core uses flags to specify the allocation rights, type, and state of each region of memory.
A. True True – Allocation rights include read, write, and execute rights. Type include memory that is private to a process, memory whose image can be seen by other processes, and memory that is mapped and therefore usable by other processes. States include free, committed, and reserved. Free meaning physical memory is available to be allocated to the process. Committed meaning that physical memory has already been allocated to the process. Reserved meaning a portion of virtual memory is reserved for a process but no real memory has been allocated.
Q. Windows CE 5.2 uses _________ and Frames to minimize internal fragmentation, limiting it to only a small fraction of the last page of a process, and eliminate external fragmentation.
A. Paging
Q. This is the common data structure used for memory management in Windows CE 5.2 Core.
A. Heap
Q. This is referred to as the object store in the Microsoft® Windows® CE environment.
A. What is the file system or data store.
Q. True of False. The file system can be either a RAM and ROM file system, or a ROM-only file system.
A. True
Q. This Acronym represents the file system currently used by Windows Mobile and is based off the FAT file system
Q. What is TFAT. (Transaction- Safe FAT File System)
Q. True or False. TFAT directories can be deleted using a Windows desktop OS.
A. False
Q. Windows Embedded CE includes file system ______ implemented as a file system filter that allows you to encrypt data stored on removable storage cards.
A. What is Encryption.
Q. The most recent version of Windows Mobile is version 6 named Crossbow. It requires a processor at this clock speed to run. (round to nearest hundred MHz) (Hint, it is between 0 MHz and 1 GHz)
A. 200 MHZ
Q. A heap is a complex data structure built on this simple data organization structure.
A. Tree. A heap is a tree that satisfies the heap property namely that the root node is always the largest value and the bottom node is always the smallest value with numerically increasing values in between.
Q. The newest version of Windows Mobile supports AEC (Acoustic Echo _____) on top of VoIP. The C in AEC means this.
A. Canceling
Q. Developers for Windows Mobile use an API based off a popular API used in other versions of windows called this.
A. WIN32 API
Q. Those involved in this project have contacted Microsoft and requested that this three letter acronym be used as the code name for the next Windows Mobile version because this acronym represents a person who is devoted to performance and does “not settle for mediocrity.”
A. MTK