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c++ - 离开范围时,我的 boost managed_shared_memory 似乎没有从内存空间取消映射

转载 作者:行者123 更新时间:2023-11-30 04:58:44 25 4
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我意识到使用 boost managed_shared_memory 我有一种奇怪的内存泄漏

在打开或创建共享内存后,一旦超出范围,我的进程持有的内存量不会减少。

这是重现问题的示例:

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <chrono>
#include <thread>
#include <iostream>

using namespace boost::interprocess;
using namespace boost::container;

int main()
{

string shMemName = "name";

// Remove shared memory to reset example
shared_memory_object::remove(shMemName.c_str());

if (true) // Local scope
{
// Create shared memory
managed_shared_memory managed_shm{ open_or_create, shMemName.c_str(), 100000000 };

// Adding something random to take up most of the place in the memory
vector<short>* sharedVector = managed_shm.construct<vector<short>>(shMemName.c_str()) ();
sharedVector->resize(40000000);
} // <--- I expect to lose access to the shared memory therefore having it unmapped

// Even if I remove the shared memory, there seems to still be a leak
bool success = shared_memory_object::remove(shMemName.c_str());

std::cout << "Done " << success << std::endl;
std::this_thread::sleep_for(std::chrono::seconds(50));

// If we check the amount of memory used by the process, it is > 80 Mb

return 0;
}

不是删除共享内存,而是使用以下删除其中的 vector 似乎可以有效地释放内存:

managed_shm.destroy<vector<short>>(shMemName.c_str());

但是,这不是我要实现的目标。我希望它仍然在内存中,只是未映射到创建它的进程。

为什么不离开范围取消映射共享内存?我是否必须做一些具体的事情,如果是的话,那是什么?

编辑:

修改示例使程序因内存饱和而崩溃:

int main()
{
string shMemName = "name";
shared_memory_object::remove(shMemName.c_str());

for (int i = 0; i < 500; ++i) // 500 should make it crash on any computer
{ // unless you have way too much RAM
// Create shared memory
managed_shared_memory managed_shm{ open_or_create, shMemName.c_str(), 100000000 };

// Adding something random to take up most of the place in the memory
vector<short>* sharedVector = managed_shm.construct<vector<short>>(shMemName.c_str()) ();
sharedVector->resize(40000000);

// Remove memory
bool success = shared_memory_object::remove(shMemName.c_str());

std::cout << "Is removal of shared memory successful ?"
<< "(If 1 yes, if 0 no) : " << success << std::endl;
}
return 0;
}

共享内存总是被删除并重新创建。它不应该泄漏任何东西……但它确实泄漏了。

最佳答案

您的 vector/实例/在共享内存中,但所有元素数据都不在。因为您不使用共享内存分配器。而不是 std::vector<T>使用 std::vector<T, myallocator>其中 myallocator从共享内存分配。

例如:

靠 Coliru 生存

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/containers/vector.hpp>
#include <iostream>

namespace bip = boost::interprocess;
using ShMem = bip::managed_shared_memory;
using Vec = bip::vector<short, bip::allocator<short, ShMem::segment_manager> >;

int main()
{
std::string shMemName = "name";
bip::shared_memory_object::remove(shMemName.c_str());

for (int i = 0; i < 500; ++i) // 500 should make it crash on any computer
{ // unless you have way too much RAM
{
// Create shared memory
bip::managed_shared_memory managed_shm{ bip::create_only, shMemName.c_str(), 100000000 };

// Adding something random to take up most of the place in the memory
Vec& sharedVector = *managed_shm.construct<Vec>("vecname") (managed_shm.get_segment_manager());
sharedVector.resize(40000000);
}

// Remove memory
bool success = bip::shared_memory_object::remove(shMemName.c_str());

std::cout << "Is removal of shared memory successful? " << std::boolalpha << success << std::endl;
}
}

请注意 remove 有一个小问题在 managed_shared_memory 的析构函数之前的循环中对象。

关于c++ - 离开范围时,我的 boost managed_shared_memory 似乎没有从内存空间取消映射,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/51540023/

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