MICO Architecture

1
MICOArchitecture Applications
2
Talk Overview

• Past, present, and future
• Development and use
• Book projects, Workshops
• CORBA Branding
• Architecture
• Micro-kernel based approach
• Application
• Zero-Copy CORBA for high bandwidth applications
  in clusters of PCs

Overview
3
MICO Overview

• MICO Mini CORBA (inspired by Minix)
• MICO MICO Is CORBA (inspired by GNU)
• Open Source CORBA implementation
• 1996 kick off as research/teaching project
• 1997 first public version
• 1998 binary distribution
• 1999 branded by OpenGroup
• 2000 text book
• 2001 2nd MICO Workshop
• Currently working towards CORBA 3 (e.g.,
  component model), security (MICOSec)

MICO Past, Present, Future
4
MICO Devel Use

• Distributed development
• CVS repository, write access by 5 maintainers
• Mailing lists with 1500 subscribers
• Major code contributions from 20 programmers
  world wide
• Industrial applications
• E.g., The Weather Channel, Lufthansa Systems
• Teaching
• E.g., Lectures and Courses at ETH Zurich, U
  Frankfurt, TU Darmstadt, U Stuttgart, San
  Francisco State University
• Research
• E.g., Zero-Copy CORBA, QoS support for CORBA

MICO Past, Present, Future
5
MICO Books

• Foundation for lectures and CORBA courses
• 1998 binary distribution _at_ MKP
• Binaries for Windows and several Unix platforms,
  tutorial, documentation
• 2000 text book in German _at_ dpunkt
• Dual (user and system) view on CORBA middleware
• 2003 merger of text book and distribution _at_ MKP
  (planned)

MICO Past, Present, Future
6
MICO Workshops

• Forum for MICO users and developers
• 1 day, invited talks
• 50-100 participants
• 1998 1st Intl. Workshop _at_ Darmstadt
• 2001 2nd Intl. Workshop _at_ Stanford
• 2003 3rd Intl. Workshop _at_ San Francisco (planned)

MICO Past, Present, Future
7
CORBA Branding

• 1999 MICO branded as CORBA 2.1 compliant by
  OpenGroup
• Test suite developed by ApTest (Ireland)
• Rather buggy, MICO as a test case

MICO Past, Present, Future
interoperability
Appl
Appl
portability
ORB
ORB
8
CORBA Branding cont.

• Tests
• Local function syntax (interface)
• Local function semantics (implementations)
• IDL Compiler (c language mapping)
• Interface Repository
• IIOP
• Open issues
• Test services?
• Coverage?
• Any better than simple empirical test?
• Ongoing (?) work at OMG and GMD Fokus to improve
  branding and develop Open Source test suite

9
Talk Overview

• Past, present, and future
• Development and use
• Book projects, Workshops
• CORBA Branding
• Architecture
• Micro-kernel based approach
• Application
• Zero-Copy CORBA for high bandwidth applications
  in clusters of PCs

Overview
10
Architecture

• Initial goal provide middleware platform for
  middleware research and teaching
• Similar to Minix (Mini Unix) in the operating
  system domain
• Requirement easy to understand, modify, and
  extend
• Clear, modular structure
• Simple, well understood interfaces
• Keep it simple
• Do not rely on complex tools

MICO Architecture
11
Architecture cont.

• Turns out that requirements help keep up with
  evolution of CORBA
• New CORBA application domains
• Embedded systems
• Nomadic systems
• ...
• Evolving CORBA standard
• New object adapters (e.g., POA)
• New interoperability protocols (e.g., SOAP)

MICO Architecture
12
Micro Kernel Approach

• Minimize ORBfunctionality
• Move functionality to
• Servers (separateprocess)
• Runtime libraries(same process)
• Extensibility adding, removing, exchanging
  servers and libraries without touching ?ORB

Micro Kernel Approach
13
?ORB Functionality

• Local request processing
• Select appropriate object adapter
• Keep track of pending invocations
• Task scheduling
• Coordinate concurrent ?ORB tasks

?ORB Functionality
14
?ORB Request Processing
Request Processing

• 1. Invocation adapter interface
• 2. Active invocation table
• 3. Object adapter registry
• 4. Object adapter interface

15
Colocated Client Server
Request Processing

• DII initiates method invocation
• POA executes method on object implementation

16
Separated Client Server
Request Processing

• IIOP Client transforms method invocation into
  network message
• IIOP Server transforms message into method
  invocation

17
Server Activation
Request Processing

• Mediator looks up or runs appropriate server and
  forwards method invocation

18
?ORB Task Scheduling

• Tasks
• Application can be caller and callee at the same
  time (distributed callbacks, nested method
  invocations)
• Process incoming and outgoing messages on
  multiple communication channels
• Requirements
• Multithreading optional (e.g., Palm OS)

Task Scheduling
19
Event Based Scheduler

• Split task into nonblocking segments
• Blocking operation at start of each segment
• E.g., wait for data from network, timeout, or
  condition (events)
• Register segmentswith scheduler
• Executes segmentwhen blockingoperation
  completes
• Non-preemptive

Task Scheduling
20
Evaluation

• CORBA suggests a modular design
• Invocation interfaces
• Skeleton interfaces
• ORB core
• Object adapters
• Most implementations melt this modular design
  into a monolithic implementation
• Changes in CORBA spec often require major ORB
  changes

Evaluation
21
Evaluation cont.

• Often easy to adopt MICO to changes in the CORBA
  specification
• Due to micro-kernel approach
• Advent of the POA
• BOA untouched
• BOA and POA coexist, even in one application
• New interoperability protocols (SOAP)
• Easy to introduce new interop protocols, even
  non-GIOP-based ones

Evaluation
22
Talk Overview

• Past, present, and future
• Development and use
• Book projects, Workshops
• CORBA Branding
• Architecture
• Micro-kernel based approach
• Application
• Zero-Copy CORBA for high bandwidth applications
  in clusters of PCs

Overview
23
Zero-Copy CORBA

• Clusters of Personal Computers (CoPs) equipped
  with Gigabit Ethernet
• Best performance, lowest price
• Many multimedia apps require fast bulk data
  transfer
• Poor memory subsystem limits overall
  communication bandwidth
• Data copies slow things down
• Aim improve end-to-end performance of bulk data
  transfers
• Christian Kurmanns PhD project at ETH Zurich

Zero-Copy CORBA
24
Performance Limits

• Pentium II 400MHz, Intel 440BX chipset, Gigabit
  Ethernet
• Network 125 Mbyte/s
• 33 MHz PCI 126 Mbyte/s
• Memory copy 92 Mbyte/s
• Memory bandwidth lt network bandwidth
• Linux-2.2 measurement 42 Mbyte/s
• Therefore eliminate data copies at all layers

Zero-Copy CORBA
25
Data Copies
ORB
Zero-Copy CORBA
TCP/IP
NIC
26
NIC Driver / Network

• Problem limited Ethernet packet size (MTU) of
  1500 bytes
• Sender fragments data stream into sequence of
  small packets
• Receiver has to reassemble stream
• Requires data copies since MTUlt memory page size
  (4k)
• Solution
• Driver pretends MTU of 4k
• (De)fragments page (3 packets)using fast DMA
  to/from NIC
• Uses speculative techniques to defragment without
  copies makes the common case fast

Zero-Copy CORBA
27
TCP/IP

• NIC driver handles whole memory pages
• Page remapping instead of copying
• TCP/IP headers are kept separate from payload
• Scatter/gather lists (DMA descriptors)

Zero-Copy CORBA
4k
28
CORBA ORB

• In heterogeneous CoPs no need to marshal data
  structures
• Transmit memory image of large data structures
  with zero copies
• Separate control from data transfer
• References instead of embedded data in GIOP
  messages

Zero-Copy CORBA
29
MPEG Transcoder

• Maximum bulk transfer rate 75 Mbyte/s (instead
  of 42 Mbyte/s)
• Example app parallel transcoding of MPEG streams

Zero-Copy CORBA
30
Summary

• Started off as research/teaching project
• Book projects, Workshops
• Developed into full-fledged CORBA implementation
• With help from the Open Source community
• Goal keep pace with CORBA standard
• Micro-kernel based architecture
• Application high bandwidth applications in
  clusters of PCs
• www.mico.org

Summary