EECS 750: Advanced Operating Systems 01/31 /2014 Heechul Yun - - PowerPoint PPT Presentation

EECS 750: Advanced Operating Systems

01/31 /2014 Heechul Yun

Administrative

• Next summary assignment due

– by 11:59 p.m., Sunday – Improving Performance Isolation on Chip Multiprocessors via an Operating System Scheduler, PACT’07

• Sign up for presentations

– First student presentation starts on Feb 3. (Monday)

• Project group

– Due on Feb 3. (Monday)

Recap: CPU Scheduling

• Unicore scheduling

– Fairness and responsiveness – Completely Fair Scheduler – BVT

• Multicore scheduling

– Partitioned scheduling – Load balancing – DWRR and global fairness

Today

• Topic: Group scheduling and resource management
• Linux’s CGROUP mechanism
• Resource Containers: A New Facility for Resource

Management in Server Systems, OSDI’99

Process Abstraction

• Basic unit for resource accounting

– E.g., cpu time spent, memory size, …

• Basic unit for scheduling
• But…

A Scenario

• Background tasks in your desktop

– E.g., BitTorrent, AntiVirus scan, create search indexes for local files, …

• Control all background tasks to consume

– Less than 10% of CPU time – Less than 20% of total memory – Less than 50% of network bandwidth – …

Another Scenario

• Tasks in a server node

– Map/reduce processes – Web server processes – Search query processing processes – …

• You want to

– Control all map/reduce processes’ resources – Control all web server processes’ resources – …

• How?

(*) Figure source: Zheng et al, “CPI2: CPU performance isolation for shared compute clusters”, EuroSys’13

Threads/server at Google(*)

CGROUP in Linux

• Control Group

– Started by engineers at Google in 2006

• Group multiple processes

– E.g., EECS750 (15 processes), EECS678 (30 processes) groups

• Control resource usage on a per-group basis

– E.g., 70% CPU to EECS750, 30% CPU to EECS678

Group Hierarchy

• Represents a tree structured relationship

among groups

Root Group Undergraduate Group Graduate Group PhD Group Master Group

Resource Management

• Control resource allocation on a per-group basis

Root Group Undergraduate Group Graduate Group PhD Group Master Group 100% CPU 100% MEM 30% CPU 50% MEM 70% CPU 50% MEM 30% CPU 30% MEM 40% CPU 20% MEM

CGROUP Subsystems

• Control resources of a CGROUP
• Available subsystems

– cpu CPU b/w limit, weight (share), … – memory memory size limit, … – cpuset cores, memory controllers, … – …

Example

# mount -t cgroup none /sys/fs/cgroup; # cd /sys/fs/cgroup # mkdir grad; mkdir grad/phd; mkdir /grad/master → create ‘grad’, ‘phd’, ‘master’ CGROUPs # # echo 100 101 > grad/phd/tasks → assign PID 100, 101 to the ‘phd’ group # echo 200 201 202> grad/master/tasks → assign PID 200, 201,202 to the ‘master’ group # echo 3072 > grad/phd/cpu.shares # echo 4096 > grad/master/cpu.shares → assign 3:4 CPU weights to ‘phd’ and ‘master’ groups

See https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt

Today’s Paper

• Resource Containers: A New Facility for

Resource Management in Server Systems, OSDI’99

Some Background

• Dot-com bubble (1997-2000)

– Many internet companies were founded

• Google: 1998, Netflix: 1997

– Every company wanted to create its website

• Web server research

– First version of Apache webserver in 1995 – High performance web server was a hot topic

• Client computing → Server computing

Classical Application

• An application = A process = A resource

principal (CPU time, memory)

Kernel Intensive Application

• Scenario: interrupt handling to receive packets for process A
• ccurred while executing process B

– Time spent on ISR will be charged to process B’s system time. – Packet buffer memory is not charged to any process

• Resources spent on kernel are not controlled

Application with Multiple Processes

• How to account and manage resources for a

group of processes?

Resource Container

• A logical abstraction to manage resources

– Resources: CPU time, memory, …

• A resource container can be associated with

multiple processes (threads)

• Can construct a hierarchy

Example

Web Server

CGI Process #1 Static documents

Container 1

Dynamic document

Container 2

CGI Process #N

Web Clients

Web Server Throughput

Summary

• Group resource management

– Generic abstraction to account and control resources

• CGROUP in Linux

– Powerful tools which are heavily used by google cloud, android, and many Linux distros

Discussion

• What resources are important?
• What resources are controllable by the OS?
• What resources are not controllable by the

OS?