Download Lazy Receiver Processing(LRP).

Lazy Receiver Processing (LRP):
A Network Subsystem Architecture for
Server Systems
Peter Druschel & Gaurav Banga
OSDI ’96
Song, yong-joo
System Software Lab, EECS, KAIST
16, November 2000
This paper provides good knowledge of Network Subsystem
and fresh approach.
Contents
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Introduction
BSD Architecture
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LRP
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Early demultiplexing
Lazy protocol processing
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UDP/TCP
Experiment
Conclusion & Critique
3
Introduction

Resource management issue
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Fairness!
under heavy load
Cf. improve latency, use full bandwidth
4
BSD Architecture
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Lower layer, higher priority
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Invest in dropped packet
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Lack of effective load
shedding
All packet in one IP queue
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Eager receiver processing
Lack of traffic separation
Use CPU time of
Interrupted process
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Inappropriate resource
accounting
5
LRP
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IP Queue -> per socket Queue
NI demultiplex packets
 NI demux
 Soft demux
Protocol processing
 at the priority of receiving
process
 lazily
6
LRP ( cont’d )
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Early demultiplexing
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problem
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Still livelock – control msg. or corrupted data
Context switching
Fair resource allocation
Lazy Receiver Processing
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Reduced context switching
Increased memory locality
7
LRP - TCP
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Reliable, flow-controlled -> LRP cannot
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Asynchronous receiver processing
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RR at the priority of app. of associated socket
CPU time is charged to associated process
Implementation : extra Kernel thread
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small extra memory overhead
8
Experiment setup
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Sun SPARC – 60MHz, 32MB
155Mbit/s ATM LAN
SBA-200 network adaptor ( include i960 )
Modified 4.4BSD-Lite
Metric

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Throughput
Latency
9
Result
10
Conclusion
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LRP architecture
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Early demultiplex
Lazy receiver processing
Case of TCP
Reduced context switching
Enhanced throughput, latency under heavy load
11
Critique
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NI channel Queue length decision
Measuring Latency
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with Same or higher priorty process
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Stable under overload?
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Apply to QoS