【C++项目】高并发内存池第六讲 当申请内存大于256K时的处理

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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); }
}

• 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;}

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);}}

直接还给堆。

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