memory

问题 Is virtually contiguous memory also always physically contiguous? If not, how is virtually continuous memory allocated and memory-mapped over physically non-contiguous RAM blocks? A detailed answer is appreciated. 回答1: Short answer: You need not care (unless you're a kernel/driver developer). It is all the same to you. Longer answer: On the contrary, virtually contiguous memory is usually not physically contiguous (only in very small amounts). Except by coincidence, or shortly after the

问题 How do I measure the amount of memory used by an executable which I run through the os/exec package in Golang? Is it better to do this through the OS itself? 回答1: You need to do this through the OS itself. If you are on plan9 or posix, Go will return the usage values from the OS for you in the structure returned by ProcessState.SysUsage(). cmd := exec.Command("command", "arg1", "arg2") err := cmd.Run() if err != nil { log.Fatal(err) } // check this type assertion to avoid a panic fmt.Println(

问题 I'm plotting some large plots in IPython QtConsole (and Notebook). These take up a lot of memory, but once they are plotted I don't need them any more and they can go. How can I free up memory? None of the following works: close() clf() cla() %reset The only thing that frees the memory is restarting the kernel , which I don't always want to do (say I worked through a long process to get to a specific point) [To be precise, %reset does free up some memory, but not as much as restarting the

问题 I'm looking for a library that will provide this type of information: RAM Swap space Number of CPUs speed (CPU MHz) Number of cores Chip type Ultimately I'll be calling into it from Java, but a C library would be fine, which I can wrap with JNI. Platforms of interest include, but not limited to, AIX, HP-UX, Solaris, Windows. Thanks! 回答1: Like you I was looking for a cross platform system info library and found this: http://code.google.com/p/geekinfo/ I didn't test it yet but it might suit

问题 I am running Hadoop map reduce job on a cluster. I am getting this error. OpenJDK Client VM warning: INFO: os::commit_memory(0x79f20000, 104861696, 0) failed; error='Cannot allocate memory' (errno=12) There is insufficient memory for the Java Runtime Environment to continue. Native memory allocation (malloc) failed to allocate 104861696 bytes for committing reserved memory. what to do ? 回答1: make sure you have swap space on your machine ubuntu@VM-ubuntu:~$ free -m total used free shared

问题 I am taking a MOOC course CS50 from Harvard. The last lecture I had was about memory allocation and pointers (two concepts which are absolutely new to me). What was taught is that malloc(10*sizeof(char)) allocates enough bytes on the heap to store 10 characters and returns a pointer to the first byte which can be saved in another variable as follows char *x = malloc(10*sizeof(char)) . To free the memory one would use free(x) . But there is another way to make a computer to reserve enough

问题 I have followed the advice available in several SO questions, like this one, in order to release MKMapView from memory - my code below - (void)viewDidDisappear:(BOOL)animated { [super viewDidDisappear:animated]; self.map.mapType = MKMapTypeHybrid; self.map.showsUserLocation = NO; self.map.delegate = nil; [self.map removeFromSuperview]; self.map = nil; self.locationManager.delegate = nil; } In part, it works, but not entirely. Let me provide some data. Below is the memory allocation recording

问题 I always thought that an statement like const int *a means a is an int pointer to const data and as such one should not be able to modify the value it points to. Indeed if you do const int a [] = {1,2,3} and then issue a[0] = 10 you'll get compiler errors. To my surprise, however, the following compiles without any warning and runs just fine. #include <stdio.h> #include <string.h> int main (){ const int a [] = {1, 1, 1}; const int b [] = {2, 2, 2}; memcpy((void*) &a[0], (const void*)&b[0], 3

问题 Could anybody explain what the subtle difference between these two notations: (*T)(nil)/new(T) and &T{} . type Struct struct { Field int } func main() { test1 := &Struct{} test2 := new(Struct) test3 := (*Struct)(nil) fmt.Printf("%#v, %#v, %#v \n", test1, test2, test3) //&main.Struct{Field:0}, &main.Struct{Field:0}, (*main.Struct)(nil) } Seems like the only difference of this one (*T)(nil) from other is that it returns nil pointer or no pointer, but still allocates memory for all fields of the

问题 I was reading the question "Raw Servlet vs. Spring MVC" and was wondering if Spring MVC might slow down or blow up the memory consumption of your application compared with raw servlet? Note: I originally asked it as a comment in the question mentioned above and was then kindly summoned to post it as a separate question. 回答1: Define "blow up". Define "slow down". Of course memory usage will be higher, and of course performance will be lower. How much higher, and lower compared to the