context-switching | 易学教程

Context switching when a thread invokes a system call

阅读更多关于 Context switching when a thread invokes a system call

问题 I have a process with multiple threads. If one of my threads invokes a system call like gettimeofday() , does the kernel only switch that thread out of context to service the system call, or does it switch the entire process (and all other threads) out of context? 回答1: Most system calls may involve a context switch (if other tasks are runnable) and switch the processor's state to kernel mode. But gettimeofday (and e.g. getpid() ) are unusual. with recent kernels they use VDSO to avoid it (and

Context Switches on Sleeping/Waiting Threads

阅读更多关于 Context Switches on Sleeping/Waiting Threads

问题 I'm trying to understand how operating systems handle context switching in different models to better understand why NIO performance is better in cases of large peaks in the number of requests. Apart from the fact that there may be a limit to the number of threads, I'm curious how blocking operations being done in those large number of requests can affect resource utilization. In a one request per thread model, say a servlet 2.5 based web application, if 499 threads are waiting for database

iOS4 - fast context switching

阅读更多关于 iOS4 - fast context switching

问题 When application enters in background running state, how much dirty memory usages is good to go. In apple video it's mentioned that the dirty memory should be reduced as much as we can. But in my App, I am using navigation controller to push and pop views. After moving from about 20 different pages, the dirty memory usages reaches 30 MB or so. Also on "dismissModalViewControllerAnimated" and "popViewControllerAnimated", dealloc is not called. I have two doubts: With how much dirty memory is

iOS4 - fast context switching

阅读更多关于 iOS4 - fast context switching

When application enters in background running state, how much dirty memory usages is good to go. In apple video it's mentioned that the dirty memory should be reduced as much as we can. But in my App, I am using navigation controller to push and pop views. After moving from about 20 different pages, the dirty memory usages reaches 30 MB or so. Also on "dismissModalViewControllerAnimated" and "popViewControllerAnimated", dealloc is not called. I have two doubts: With how much dirty memory is acceptable to go live? What is the alternate of navigation controller to support back button? Thanks in

How long is the time frame between context switches on Windows?

阅读更多关于 How long is the time frame between context switches on Windows?

问题 Reading CLR via C# 2.0 (I dont have 3.0 with me at the moment) Is this still the case: If there is only one CPU in a computer, only one thread can run at any one time. Windows has to keep track of the thread objects, and every so often, Windows has to decide which thread to schedule next to go to the CPU. This is additional code that has to execute once every 20 milliseconds or so. When Windows makes a CPU stop executing one thread's code and start executing another thread's code, we call