Wenjin Xu

BasicsAllocationCollectionFinalization GC Mode Sample

Idea Automatic memory management Terms Domain, Heap, Generation 0, Generation 1, Generation 2, Large object heap

Initial CLR reserve memory for small object heap and large object heap(16MB / 64MB) newobj Allocate memory from heap

When Generation 0 is full Call GC.Collect() Low memory How Assume all objects are garbage Mark following object are reachable: Static fields Method parameters Local variables CPU registers Strong References Collect

When Generation 0 is full Call GC.Collect Low memory AppDomain unload CLR is shutting down

10 GC WorkstationServer Concurrent Collections “Normal” Background GC

Single processor should use default Mode

In background garbage collection, ephemeral generations (0 and 1) are collected as needed while the collection of generation 2 is in progress

High priority thread GC together, so garbage collection is faster Server garbage collection often has larger size segments

Why do we need pinning Interop with unmanaged code How objects get pinned GCHandleType.Pinned Allowed by language syntax, eg. fixed in c# Args get pinned by the interop frame Fragmentation problem

Can not disable after enable Global Performance hunt (about <1%) Does not count memory from Marshal.AllocHGlobal

Strong Reference Allocate Memory by Marshal

查看性能计数器 使用对象池节省新建对象造成的 GC 压力 使用 VSTS 检查内存分配情况 WinDBG + sos Debug vs Release

Performance Counter us/library/x2tyfybc.aspx us/library/x2tyfybc.aspxBook CLR via C# 3 rd Edition Source Code k.aspx k.aspx