cs6235- - Efficient Packet Processing in...

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Unformatted text preview: Efficient Packet Processing in User-Level OSes: A Study of UML Younggyun Koh Calton Pu Sapan Bhatia Charles Consel College of Computing Georgia Institute of Technology Atlanta GA 30332-0280 USA LaBRI/INRIA ENSEIRB, 1 Ave. de Dr. Albert Schweitzer 33402 Talence France {young, calton}@cc.gatech.edu {bhatia, consel}@labri.fr ABSTRACT Network server consolidation has become popular through recent virtualization technology that builds secure, isolated network systems on shared hardware. One of the virtualiza- tion techniques used is that of User-level Operating Systems. (ULOSes) However, the isolation and security they bring comes at the price of performance, as virtualization intro- duces a number of overheads into the system. Such over- heads can be surprisingly large, especially for complex OS modules like network protocol stacks. Our studies of the TCP/IP stack in User-mode Linux (UML), an implementation of a ULOS, attribute the resulting slow-downs to three main sources: the execution of privileged code, memory manage- ment across layers, and additional instructions to execute. To mitigate these bottlenecks, we present five optimization techniques, improving the network performance significantly, reducing packet processing latency by 60% and increasing network throughput by three folds. Furthermore, the network throughput of the improved ULOS is comparable to that of native Linux up to gigabit speeds. 1. INTRODUCTION Server consolidation is increasingly being consid- ered as an important solution to implement complex internet services in untrusted environments. Server consolidation provides high server utilization with low hardware cost, increased manageability and easy ex- pandability, while still maintaining strong isolation amongst individual services. [21] System virtualization using user-level operating systems (ULOSes) [11][13][15][29][30] is a popular choice for implementing server consolidation. ULOSes are operating systems that run over other operating system kernels as user processes. A ULOS not only offers the advantages of typical virtual machine moni- tors (VMMs) [2][8][14][25][26] but also provides ad- ditional features such as easy installation, fine-grained configuration, and powerful diagnosis with the support of host OS tools. On the negative side, ULOSes suffer from signifi- cant performance penalties for obvious reasons: run- ning at user level, they must invoke the underlying host OS kernel to provide kernel services that cannot be emulated. While this indirection provides strong isolation, it introduces overhead considered to be unavoidable. From the server-consolidation point of view, it significantly increases the packet-processing it significantly increases the packet-processing over- head, reducing the maximum network throughput and increasing packet latency....
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This note was uploaded on 10/10/2010 for the course CS 6235 taught by Professor Staff during the Fall '08 term at Georgia Institute of Technology.

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cs6235- - Efficient Packet Processing in...

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