Evers Chen Email & Phone Number

中国 上海

Shanghai

Jemalloc深入分析：1. 深入分析了两种bitmap，tree和非tree方式的查找算法和实现原理2. 分析了paring heap，配对堆的使用，提高排序效率的实现3. RB tree 红黑树，对这个算法进行了注释4. 详细分析了Tcache实现机制5. 支持原子操作的线性同余伪随机数生成器6. 动态头长度的计算过程map_bias7. Region size设计以及和index对应关系8. radix tree基数树9. 通过jemalloc的实现学习，进行了一些高可靠性编程的讨论10. small/large/huge内存的分配和释放过程 Vowifi协议栈内存和缓冲区的优化：1）经过12.1，12.2，12.3三项优化，百分比如下：Native Heap内存降低 6476-5208/6476=1268/6476=19.6%Total 内存降低 24699-23543/24699=1156/24699=4.7%12.1 Dbuf ZOS_DBUF_SIZEOF_DATA（24字节）导致的内存浪费 25.6%12.2 Dbuf 双重pool分配内存浪费问题 48%12.3 用系统的jemalloc取代pool进行分配内存优化 23.4%2）Je_free(p+n)问题导致的踩内存，当调用je_free的时候用，不是拿分配的时候的地址，而且有一定的往后偏移的时候，这个时候jemalloc会只释放后半部分，前半部分保留。（主要问题还是分配和释放的函数不匹配造成的）3）Zos_DlistRemove/Zos_PoolAlloc的 crash问题，这两个crash的root cause都是操作pool的stFreeNodeLst/stAllocLst导致的问题，这个原因可以在dlist加mutex来修复。4）IKE stMsgList 释放的踩内存地址问题修复。pstMsg的结构体内存是在zMemBuf里分配的，所以在内存delete后进行的pstMsg->zMemBuf = NULL;操作是在已释放内存区，这是非法的操作。5）Dbuf的dump部分crash，是因为多线程操作dump list导致的，这边没有做多线程互斥访问。6）这个bad fix会导致很大一部分dbuf内存永远得不到释放，会滞留在内存。同时，这个也不能完全避免crash，因为有部分其他分支的dbuf在释放的时候还是存在crash的可能。7）内存泄漏：Udp接收缓冲区内存和pstEvnt->pstMsg内存的不释放问题8）内存分配和释放方式的匹配问题：当URI的获取方式改变，内存不再是由Zos_SysStrAlloc分配时，不能由SysStrFree去释放。9）修复了几个因为提供错误内存句柄导致的释放失败问题10）对于循环内部有删除节点的情况，FOR_ALL_DATA_IN_DLIST是不安全的，存在crash风险，应该使用FOR_ALL_DATA_IN_DLIST_NEXT，11）修复了错误的sbuf page size的配置导致配置文件load失败。VoIP client, VoLTE system design on Android, End to End VoWiFi, VoLTE, and Handover between them，IPSEC process of VoWiFi.

中国 上海市区

Product: VoIP access network (Cable Modem Termination System)Deeply understand Packetcable architecture, Packetcable implementation of DQoS and Packetcable implementation of PCMM. Familiar with COPS and NCS protocol, Familiar with Cisco CMS product BTS which interaction with CMTS as soft-switch.Responsibilities:  System analyses, Code, and Function analysis, Implementation  VoIP, PacketCable and PCMM interact with call manager system and policy server. Load Balance feature development and maintenance. IXIA and pagent tools were used to generate traffic for test purpose. Multicast of CMTS field development. VoIP maintenance for CMTS.

Shanghai City, China

Product: VoIP core network (Media Gateway Control)Project : MGC HOST Environment（Research and development） Initial version of HOST, actually it’s a SIS simulator, not mgc simulator, and MGC is not working at all. Setup mgc environment to start-up it, all the mgc running parameters (xml files) and system parameters (configuration files), the real target environment is GUI based. Setup seagull simulator and the scenario (configuration) files for both client and server, to work as client/server with MGC/PSTN.  Create stub for ISUP and SCTP AL, it’s ss7 simulator and MGW simulator actually, MGW simulator support register and call related function ADD/Modify/Subtract, and it support video call as well, the h245 message handled and response properly. Optimizer: speed issue, for network boot up NFS, find solution for it and make it upgrade smoothly.  Capacity test improvement, mainly on SS7 and MGW simulator, the HOST capacity has been increased from 1cps to 150cps, make it possible to test high performance test case. Auto test environment setup, design and setup from scratch and it’s the first auto test environment of MGC, it can found bug in the early phase and save lot’s of man hour for manual regression test. Project other features: Developed feature: Mobile MGW, Manually continuity check, LI, Number Portability, Virtual MGC (multi sip profile), PSTN Load balanceResponsibilities: System analyzes, Code, and Function analysis, Implementation Develop and Setup MGC host environment for all the designers. CPBS (OS and 3pp components, also new hardware) upgrade. Handle MGC DM issue from customer site. As mentor of newcomer.  Excellent employee of 2007

Master'S Degree, Cs

学士, Chemical Engineering