6/10/2005 fastos pi meeting/workshop k42 internals dilma da silva for k42 group ibm tj watson...
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6/10/2005 FastOS PI Meeting/Workshop
K42 Internals
Dilma da Silva for K42 group
IBM TJ Watson Research
6/10/2005 FastOS PI Meeting/Workshop
K42 Goals
• Scalability
• Flexibility/customizability
• Framework for OS research– Linux API and ABI and kernel module compatible– Available to collaborators under LGPL
• Maintainability/extensibility
6/10/2005 FastOS PI Meeting/Workshop
Structure
• OS function in user-level library– examples: timers, thread
library...– allows OS services to be
customized for applications with specialized needs
– avoids interactions with kernel/servers, reduces space/time overhead in kernel/servers
• Object-oriented design at all levels Micro-kernel
Servers
Linux emulation
OS lib
Application
Linux emulation
OS lib
Application
6/10/2005 FastOS PI Meeting/Workshop
Object-oriented design
standard OS
webserver database
parallel application web
server database
parallel application
6/10/2005 FastOS PI Meeting/Workshop
OO Design: MM Objects
Process
FCM
FCM
FR
FR
HAT
RegionRegionRegion
RegionRegion
FCM: File Cache ManagementFR: File RepresentativeHAT: Hardware Address Translation
6/10/2005 FastOS PI Meeting/Workshop
Process
FCM
FCM
FR
FR
Region
Region
Process
FCM FRRegion
Region
6/10/2005 FastOS PI Meeting/Workshop
Region Region Region Region
Region Region
• OO design enables specialized implementations
Specialization and Clustered Objects
6/10/2005 FastOS PI Meeting/Workshop
Clustered object infrastructure
• Per-processor level of indirection avoids any centralized bottleneck
• Provides library to simplify distributed implementation– Caching of local state– Incremental distribution of services– DHash
Focus on locality!• Read-Copy-Update techniques
– Use non-blocking synchronization– Avoid locking hierarchies
6/10/2005 FastOS PI Meeting/Workshop
Hot-swapping
• change one system component/type for another without bringing system down
• potential uses– scalability– performance– monitoring– extensibility– testing
• Dynamic update: system availability
6/10/2005 FastOS PI Meeting/Workshop
Hot-Swapping/Dynamic Update
• Depends on:– object-oriented structure of system– technology to establish a quiescent state– level of indirection
• Implementation has no additional overhead– when not swapping an object– for objects not being swapped
• Limitations:– is not instantaneous– initial prototype– Current work: coordinated swapping, interface changes, external
policies...
6/10/2005 FastOS PI Meeting/Workshop
Independent workloadsmodified SDET
0
5000
10000
15000
20000
25000
30000
35000
40000
-1 4 9 14 19 24
Processors
Scri
pts
/H
ou
r
Linux
K42
Parallel PostMark
0
2
4
6
8
10
12
14
16
18
-1 4 9 14 19 24
Processors
Speedu
p
LinuxK42
Parallel Make (flex)
0
5
10
15
20
25
-1 4 9 14 19 24
Processors
Speedu
p
LinuxK42
6/10/2005 FastOS PI Meeting/Workshop
More hot-swapping
0
20
40
60
80
100
120
140
160
180
0 1 2 3 4 5 6
Number of concurrent background streams
SDET
thro
ughp
ut (s
crip
ts/h
our)
LRU
Adaptive
0
200
400
600
800
1000
1200
1400
1600
1800
Shared Shared-Exclusive Shared-Exclusive /Small-Large
Tran
sact
ions
per
sec
ond
Adaptive paging Adaptive file imp.
6/10/2005 FastOS PI Meeting/Workshop
Memclone benchmark: Memory intensive parallel application
0
500
1000
1 5 9 13 17 21
Linux 2.4.21
K42
0
500
1000
1 5 9 13 17 21
ms
ec
pe
r th
rea
d
All MM objects distributed
All MM objects shared
6/10/2005 FastOS PI Meeting/Workshop
Performance monitoring
Emulation Layer FaultsFork-Child Faults
Process Init Faults
K42 App Faults
Emulation Layer
Process Init
Fork-Child SetupMisc. Kernel Time
Process CleanupK42 App Time
Linux User App Faults
Linux User App Time
• unified cheap scalable non-blocking tracing infrastructure for correctness and performance debugging
• key parts of design transferred to LTT• post processing tools easy to develop: lock contention, sampling, time
breakdown, visualization, caching effects, ... • in final numbers, disabled, but only %1.6 difference UP and 24 way