virtual-memory

问题 My compilation fails on ubuntu 12.10 with 300mb memory available (750mb total, 350mb to MySQL), 1.5ghz, I am trying to rework wt's basic hello world file into a simple ajax page. I'm pretty sure it's not a memory issue at heart since I was able to compile the original hello.C file with g++ -O3 -o hello hello.C -lwtfcgi -lwt -lboost_signals . I'm sure I'm screwing up the c++ since I ripped out the guts of HelloApplication::HelloApplication(const WEnvironment& env) : WApplication(env) and put

问题 I would like to know architectures which violate the assumptions I've listed below. Also, I would like to know if any of the assumptions are false for all architectures (that is, if any of them are just completely wrong). sizeof(int *) == sizeof(char *) == sizeof(void *) == sizeof(func_ptr *) The in-memory representation of all pointers for a given architecture is the same regardless of the data type pointed to. The in-memory representation of a pointer is the same as an integer of the same

问题 I'm writing an application that encrypts its data. It can then display it unencrypted using the app's UI after a user enters password. My goal is to minimize exposure of plaintext data while in RAM. For that I want to prevent swapping it to disk as much as possible. I know that I can adjust my process's working set (by calling SetProcessWorkingSetSize API) and then lock those sensitive pages in RAM (by calling VirtualLock.) That, in theory, should minimize the chances of it being written to

问题 This question was asked to one of seniors in a programming interview. According to me, because the sizes of memory accessed by softwares are increasing, the memory may soon be exhausted. So in this case if we used swapping, it would be inefficient. So we would go for virtual memory because it maps the memory in the disk to the main memory. But if we can have very huge memory then would virtual memory be of use? And please tell if the above answer needs some modifications. 回答1: Virtual memory

问题 The blocking VM performance is better overall, as there is no time lost in synchronization, spawning of threads, and resuming blocked clients waiting for values. So if you are willing to accept an higher latency from time to time, blocking VM can be a good pick. Especially if swapping happens rarely and most of your often accessed data happens to fit in your memory. This is default mode of Redis (and the only mode going forward I believe now VM is deprecated in 2.6), leaving the OS to handle

问题 What is the difference between reserve argument and commit argument to CreateThread Windows API function? I can't understand the following lines .. The reserve argument sets the amount of address space the system should reserve for the thread's stack. The default is 1 MB. The commit argument specifies the amount of physical storage that should be initially committed to the stack's reserved region. these two lines you will find them in this paragraph which explains one of the parameters of the

问题 What does the virtual memory space size depend on? Does it depend on the RAM or on the architecture or something else. 回答1: Basically it depends on the architecture (32bit 64bit and so...). This is a very simplistic explanation of things, but so called "architecture" limits size of the virtual address space. For example, 32bit architecture will enable to address 2^31 memory addresses. The size of the RAM will limit the amount of physical memory that can be used, but not the virtual address

问题 When I'm on SO I read a lot of comments guiding (Especially in C) "dynamic allocation allways goes to the heap, automatic allocation on the stack" But especially regarding to plain C I disaggree with that. As the ISO/IEC9899 doesn't even drop a word of heap or stack. It just mentions three storage duriations (static, automatic, and allocated) and advises how each of them has to be treat. What would give a compiler the option to do it even wise versa if it would like to. So my question is: Are

问题 I am writing a C++ program that essentially works with very large arrays. On Windows, I am using VirtualAlloc to allocate memory to my arrays. Now I fully understand the difference between reserving and committing memory using VirutalAlloc; however, I am wondering whether there is any benefit in committing memory page-by-page to a reserved region. In particular, MSDN (http://msdn.microsoft.com/en-us/library/windows/desktop/aa366887(v=vs.85).aspx) contains the following explanation for the MEM

问题 I am stuck with an issue in my app. I have been testing up until now mostly on my iPad 3 with occasional checks on my iPad 1 to make sure all is well. I am playing a UIImageView animation in my app and it keeps quitting with only a "Received memory warning" message before it quits. I have been using the Object Allocations tool in instruments but according to that, my memory usage is way low. So after researching for a bit I came across this post by Mr. Larson: https://stackoverflow.com/a