memory-management

问题 So, here's the code for my cellForRowAtIndexPath: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"identifier"]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"identifier"]autorelease]; } NSInteger artistIndex = 1; // 1 NSInteger albumIndex = 3; // 3 NSInteger dateIndex = 6; // 6 NSInteger imageIndex =

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Where are the best explanations of memory management for iPhone? I come from a web development background. I'm good at XHTML, CSS, JavaScript, PHP and MySQL, because I use all of those technologies at my day job. Recently I've been tinkering with Obj-C in Xcode in the evenings and on weekends. I've written code for both the iPhone and Mac OS X, but I can't wrap my head around the practicalities of memory

问题 When is the string literal "hello" allocated and deallocated during the lifetime of the program in this example? init(char **s) { *s = "hello"; } int f() { char *s = 0; init(&s); printf("%s\n", s); return 0; } 回答1: The string literal is initialised into read-only memory segment by the compiler. There is no initialisation or removal done at run-time. 回答2: They are not allocated but instead stored in the DATA segment of the executable. 回答3: Assuming there is an operating system, the memory

问题 This question already has answers here : Closed 9 years ago . Possible Duplicates: Malloc a 3-Dimensional array in C? dynamic allocation/deallocation of 2D & 3D arrays How can i allocate 3D arrays using malloc? 回答1: array = malloc(num_elem * num_elem * num_elem * sizeof(array_elem)); Why not? :) 回答2: There are two different ways to allocate a 3D array. You can allocate it either as a 1D array of pointers to a (1D array of pointers to a 1D array). This can be done as follows: int dim1, dim2,

问题 I know how to get CPU usage and memory usage for a process, but I was wondering how to get it on a per-thread level. If the best solution is to do some P-Invoking, then that's fine too. Example of what I need: Thread myThread = Thread.CurrentThread; // some time later in some other function... Console.WriteLine(GetThreadSpecificCpuUsage(myThread)); 回答1: Here's an example which does what you want http://www.codeproject.com/KB/system/processescpuusage.aspx 回答2: As said, memory use cannot be

问题 Let's say that I have a loop that returns a bunch of autoreleased NSData objects... NSData* bigData = ... while(some condition) { NSData* smallData = [bigData subdataWithRange:...]; //process smallData } Under ARC, should I still wrap an @autoreleasepool around the while condition? NSData* bigData = ... @autoreleasepool { while(some condition) { NSData* smallData = [bigData subdataWithRange:...]; //process smallData } } The reason why I'm asking is I see the living allocation count in

问题 Let's say that I have a loop that returns a bunch of autoreleased NSData objects... NSData* bigData = ... while(some condition) { NSData* smallData = [bigData subdataWithRange:...]; //process smallData } Under ARC, should I still wrap an @autoreleasepool around the while condition? NSData* bigData = ... @autoreleasepool { while(some condition) { NSData* smallData = [bigData subdataWithRange:...]; //process smallData } } The reason why I'm asking is I see the living allocation count in

问题 If I use the Runtime class ( freeMemory() , totalMemory() , and gc() ), then it gives me memory above MB (i.e. 1,000,000 bytes). But if I run the same code on any online compiler, then they show memory used in KB (i.e. 1000 bytes). This is a huge difference. This means Runtime does not show the actual memory used by the program. I need to calculate actual memory used by the program. What is the way these online compilers use to calculate memory used by the program? 回答1: First calculate the

问题 Is there any suitable way to get the physical address by the logical one except to walk through page directory entries by hand? I've looked for this functionality in kernel's sources and found that there is a follow_page function that do it well with built-in huge and transparent-huge pages support. But it's not exported to kernel modules (why???)... So, I don't want to invent the wheel and I think that it's not very good to reimplement the follow_page functionality by hand. 回答1: Well, it

问题 I have been told this many times. But I don't know WHY...What extra cost is involved when allocating memory from heap? Is it hardware related? Is it related to CPU cycles? So many guesses but no exact answers...Could someone give me some elaboration? Just as "unwind" said, the Heap data structure is more complicated than Stack. And In my opinion, some memory space is allocated to a thread as its Stack when it starts to run, while the heap is shared by all the threads within a process. This