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Class-based prioritized resource control in Linux

Amit Khanna

Roll No 4134, BE - I

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Outline

Motivation Framework Classification Engine (CE) Resource Schedulers Resource Monitoring User Interface Conclusion and Future Work

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Introduction

Workload Any system work with a distinct business goal A set of kernel tasks executing over some

duration Vary in their importance Resource demands

Diverse Dynamically changing

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Workload Management

Current scenario Manual Static

Workload Managers (WLM) Differentiated service Translate business goals to system goals Ability to handle dynamically changing

resource requirements

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Class-based Kernel Resource Management (CKRM) Class - A dynamic grouping of OS objects

Entitlements Reclassification of a task Hierarchical

Classification Rule - Method by which a task can be classified into a class

Policy - A collection of class definitions and classification rules

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Components of CKRM

Core Defines the basic entities Link between all the other components

Classification Engine (CE) Classifies kernel objects into classes

Class-aware Resource Controllers RCFS (Resource Control File System)

User-Kernel interface for CKRM

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Components of CKRM

UserKernel

Resource Management Middleware

System Administrator

Classification Filesystem

RCFS (Resource Control Filesystem)

CKRM API

Externally defined Policy--Rules -- Class defs

Classification EngineCKRM Core

fork()exec()…

Share Usage(per- resource)

Class AT1

T2

T4

Share Usage(per- resource)

Class DT4

Reclassification

Class Aware Patches

Resource SchedulersCPU, Disk I/O, Network,

Memory

Class Aware Resource Allocation

Ti - Tasks- Patches

Resource request

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Classification Engine (CE)

Optional component (module) Automatically triggered on kernel events

Eg. setuid, fork, exec RBCE (Rule Based Classification Engine) Rule format

A set of attribute-value tuples (A, V) and a class C

Eg gid=10, uid = 7, target = /rcfs/task_class/Gold

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CPU Controller

Current scheduler - O(1) scheduler One runqueue per CPU Active array and expired array 140 nice levels

Extensions Runqueues for each class for each CPU Hierarchical scheduling scheme ecp(C) = R * Σ cycles(C)/share(C) + top_prio

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Test Results

Class shares

•Gold – 60%

•Silver – 30%

•Bronze – 9%

•Best Effort – 1%

Nice Values : -20, -10, 0, 10, 19

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Memory Controller

Current Scenario Memory zones Page descriptor lists – active, inactive and free Page reclamation

Extensions Classes have associated share of physical memory No of pages allocated to a class are monitored Class shares are enforced only when system memory

is low Modified page reclamation

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Memory Usage Test Results

Test conducted on a 2.4GHz Pentium 4 desktop running Redhat Linux 9 and the 2.5.69 Linux kernel running using a simple microbenchmark

Total physical memory = 352 MB

Class A’s access freq = 2 * Class B’s access freq

Class A’s consumption = Class B’s consumption = 200 MB

Class A’s share/Class B’s

share

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Resource Monitoring

State-agent Runs in user-space Maintains state of existing and exited processes

Monitoring infrastructure design principles Event-driven

Aperiodic Periodic

Communication channel Minimal kernel state

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Resource Monitoring (continued)

Sampling Self-restarting kernel timer Struct delay_info Schedulers records timestamps Kernel module sends data to state-agent as

records

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Resource Control File System (RCFS)

/rcfs

/rcfs/task_class/rcfs/

socket_class /rcfs/ce

Files

member

config

target

shares

stats

Files

reclassify

state

Rules

Gold Music

Compile

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Conclusions and Future Work

Goal-oriented WLMs can automate low-level administration

Critical workloads can be protected from workload pressure by specifying their minimum shares

Redeveloping resource controllers to support hierarchy of classes

Cooperative communication between various resource controllers

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References

CKRM Open Source Project. Class-based kernel resource management. http://ckrm.sf.net/

Enabling Autonomic Workload Management in Linux, IEEE Proceedings, International Conference on Autonomic Computing (ICAC'04), 17-18 May 2004, Pages: 314 – 315

AIX 5L Workload Manager, IBM Corp.http://www.redbooks.ibm.com/redbooks/pdfs/sg245977.pdf

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Scheduling Overhead

Test results have been measured using LMBench benchmark

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Figure 10: Monitoring and Control Approach

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for (i=0; i<50; i++)

{ start = get_time();

busy_waiting(N);

end = get_time();

response = end - start - N;

sleep(200) ;

}

Interactivity Test Code

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Interactivity Test Results

Gold, Bronze and Best Effort classes have 5 CPU bound jobs.

Silver class has an interactive job

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I/O Controller

Current scenario Each block device has a single logical queue Merges and sorts I/O requests made by block

layer Passes on the request to device driver

Extensions One queue per-class Moves the requests from input queue to

dispatch queue in proportion of their weight

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I/O Controller

CKRM I/O Scheduler

Block Layer (Producer)

Low Level Device Driver (Consumer)

Output Queue

FCFS

Dequeue Function

Sort/ Merge

Enqueue Function

Per-class queues