iPhone / iPad IOS App仪器内存计数与task_info内存计数 [英] iPhone / iPad IOS App Instrument Memory Count vs. task_info Memory Count

问题描述

我一直在使用仪器泄漏测试仪，它为应用程序提供了大约1-3兆的总分配数。

I have been using the Instruments Leak Tester and it gives a number for Total Allocations for an app around 1-3 meg.

但是，当使用task_info时报告更大的内存量，如10-20 meg。

But, when using the task_info it is reporting much larger memory amounts like 10-20 meg.

我想我只想确认task_info是否返回某种总内存，包括堆栈/等等泄密测试仪只是报告了Malloc / Alloc内存。

I guess I just want to confirm that the task_info is returning some sort of total memory including stack / etc where the leak tester is just reporting Malloc / Alloc memory.

另外，为什么在应用程序期间，当泄漏测试仪没有增加那么多时，task_info数量会增加很多。 ...

Also, why would the task_info number be increasing quite a bit during the app when the leak tester is not increasing that much....

    struct task_basic_info info;
    mach_msg_type_number_t size = sizeof(info);
    kern_return_t kerr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&info, &size);
    if( kerr == KERN_SUCCESS ) {
    NSLog(@"Memory in use (in bytes): %u", info.resident_size);
    } else {
      NSLog(@"Error with task_info(): %s", mach_error_string(kerr));
    }

推荐答案

这些数字无法真正比​​较。甚至属于（共享的）存储器映射文件（例如库）的页面也将被视为该任务的驻留页面。但泄漏测试仪会忽略它们。

Those numbers cannot be compared really. Even pages belonging to a (shared) memory mapped file (e.g. a library) will count as resident pages for the task. But they will be ignored by the Leak Tester.

需要注意的重要一点是，过程可用的内存之间存在概念上的差异（以任何方式：readonly，读/写，可执行或不可执行）和您在程序中分配的内存。并非所有可用内存都连接到您所做的实际分配（例如共享库），并且您分配的所有内存都不一定驻留在内存中（例如，大型malloc不会立即为您保留物理内存，但只能立即为它使用）。

The important thing to note is that there is a conceptual difference between memory available to the process (in whatever way: readonly, read/write, executable or not) and memory allocated by you, within your program. Not all available memory is connected to an actual allocation you did (e.g. a shared library) and not all memory you allocate is necessarily resident in memory (e.g. a big malloc will not reserve physical memory for you right away, but only as soon as it is used).

您可以使用以下方法测试内存（或文件）的匿名区域来测试其影响：

You can test the impact of this by mapping an anonymous region of memory (or a file) using:

#include <sys/mman.h>

// allocate anonymous region of memory (1 mb)
char *p = mmap(NULL,1024*1024,PROT_WRITE|PROT_READ,MAP_PRIVATE|MAP_ANON,0,0);

// actually access the memory, or it will not be resident
int sum=0;
for(int i=0;i<1024*1024;i++ ) sum += p[i];

您可以轻松将其更改为 mmap a通过将fd传递给 mmap 并将 MAP_ANON 更改为 MAP_FILE 。

You can easily change this to mmap a file, by passing an fd to mmap and changing MAP_ANON to MAP_FILE.

另外，大概是泄密测试仪从 malloc （库）调用开始直到相应的免费，而实际的内存预留只需降低一级，例如使用 mmap （系统）调用就像上面那样。

Also, presumably the leak tester looks from the malloc (library) call onward until a corresponding free, while the actual memory reservation is done just one level lower, e.g. using a mmap (system) call just like the one above.

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