【C++项目】高并发内存池第六讲 当申请内存大于256K时的处理

项目源代码：高并发内存池

1.申请过程

当申请的内存大于256kb时直接向堆中申请：

static void* ConcurrentAlloc(size_t size)
{
	if (size > MAX_BYTES)
	{
		size_t alignSize = SizeClass::RoundUp(size);
		size_t kpage = alignSize >> PAGE_SHIFT;
		PageCache::GetInstance()->_pageMtx.lock();
		Span* span = PageCache::GetInstance()->NewSpan(kpage);
		span->_objSize = size;
		PageCache::GetInstance()->_pageMtx.unlock();
		void* ptr = (void*)(span->_pageId << PAGE_SHIFT);
		return ptr;
	}
	else
	{
		//通过TLS每个线程无锁的获取自己专属的ThreadCache对象
		if (pTLSThreadCache == nullptr)
		{
			
			//pTLSThreadCache = new ThreadCache;
			static ObjectPool<ThreadCache> tcPool;
			pTLSThreadCache = tcPool.New();
		}
		//cout << "id:" << std::this_thread::get_id() << " pTLSThreadCache :" << pTLSThreadCache << endl;
		return pTLSThreadCache->Allocate(size); 
	}
}
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• NewSpan
  

//获取一个K页的span
Span* PageCache::NewSpan(size_t k)
{
	assert(k > 0 );
	//大于128页的直接向堆申请
	if (k > NPAGES - 1)
	{
		void* ptr = SystemAlloc(k);
		//Span* span = new Span;
		Span* span = _spanPool.New();
		span->_pageId = (PAGE_ID)ptr >> PAGE_SHIFT;
		span->_n = k;
		//_idSpanMap[span->_pageId] = span;
		_idSpanMap.set(span->_pageId, span);
		return span;
	}

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2.释放过程

static void ConcurrentFree(void* ptr)
{
	assert(pTLSThreadCache);
	assert(ptr);
	Span* span = PageCache::GetInstance()->MapObjectToSpan(ptr);
	size_t size = span->_objSize;
	if (size > MAX_BYTES)
	{
		
		
		PageCache::GetInstance()->_pageMtx.lock();
		PageCache::GetInstance()->ReleaseSpanToPageCache(span);
		PageCache::GetInstance()->_pageMtx.unlock();
	}
	else
	{
		pTLSThreadCache->Deallocate(ptr, size);
	}

	
}

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直接还给堆。