UTOPIA A CONTEXT-BASED SCHEDULER, FOR XEN, TO ENHANCE PERFORMANCE ISOLATION AND IMPROVE I/O RESPONSIVENESS

GROUP MEMBERS:1. Amod Jaltade2. Hormazd Billimoria3. Varun Tibrewal4. Mahesh Sharma

Pune Institute of Computer Technology (PICT), Pune

Problem Definition :

To design a non-intrusive scheduler scheme– To enhance I/O responsiveness in mixed workload

environment. – To bring about performance isolation amongst

virtual machines.

Background Concepts:• Xen - Popular open-source hypervisor• Split I/O driver model

Weight = 256

Cap = 0

Time (ms)

Tick period = 10ms

Accounting period = 30ms

CREDIT SCHEDULER

CREDIT SCHEDULER

• Three states – Under, Over, Boost• A domain is BOOSTED when it receives an

event over an event channel while it is in Under state.

UNDER STATE OVER STATE

EVENT

BOOSTED

DOM3DOM1

I/O requestDOM1

DOM1 IDD DOM2

DOM1 Scheduled

DOMAIN NAME

DOMAIN WORKLOAD TYPE

DOM1 MIXED WORKLOAD

DOM2 CPU BOUND WORKLOAD

DOM3 CPU BOUND WORKLOAD

I/O response

IDD DOM2 DOM3 DOM1

IDD ScheduledIDD reads I/O requests and creates responses

DOM1

IDD

DOM1

IDDDOM2 DOM3 DOM1

DOM2 ScheduledDOM1

DOM2

DOM3DOM3 DOM1 IDD

DOM3 ScheduledDOM1

DOM2

Solution to the problem?

DOM3DOM1

I/O request

DOM1 IDD DOM2

DOM1 ScheduledDOM1

00x111100x111200x1113

00x1323 00x3413 00x1113

DOM1• 00x384F242A

I/O response

IDD DOM2 DOM3 DOM1

IDD Scheduled

IDD reads I/O requests and creates responses DOM1

IDD

DOM1

00x1323 00x3413 00x1113

DOM1• 00x384F242A

IDDDOM2 DOM3

DOM1

DOM1

Priority is Boosted

00x1323 00x3413 00x1113

DOM1• 00x384F242A

IDDDOM1 DOM2 DOM3

DOM1 is boosted only for I/O responseDOM1

Reads response

Priority is Boosted

00x1323 00x3413 00x1113

DOM1• 00x384F242A

WORKS onReceived PacketsIDD ScheduledIDD reads I/O requests and creates responses.

IDDDOM1 DOM2

Packets to be processed

IDDDOM1 DOM2

Packets to be processed

DOM1

Reads packets

DOM2 DOM1DOM2 IDD

Packets to be processed

Reads packets

• What happened in the previous animation?

DOM1 requested a lot of I/O.The IDD worked a lot processing I/O for DOM1.DOM2 suffered as a result of this.

Conclusion :-The work done by IDD for a DOM is not pinned

to the DOM at all.

SOLUTION ?

WORKS on received packets

IDD IDD DOM1 DOM2

DOM1 IDD Credits

DOM2 IDD Credits

Packets to be processed

DOM1’s IDD credits are over. Any incoming

packets are now dropped.

DOM1 DOM1 DOM2 IDD

Packets to be processed

DOM1’s IDD credits are over. Any

incoming/transmitted packets are now

dropped.

Transmits packets.

Reads packets

DOM2 DOM2 IDD DOM1

Packets to be processed

Reads packets

Transmits packets.

DOM3iperf Server

Iperf Client

DOM2DOM1

DOM4 DOM5

Iperf Test:

1st Run 2nd Run 3rd Run 4th Run 5th Run0

2

4

6

8

10

12

14

16

18

20

0.97 0.933 1.08 1.02 0.817

15.4

17.9

15.7

17.115.9

Credit SchedulerUtopia

Average :

Credit : 0.964Mbps

Utopia : 16.4Mbps

Improvement:

1601 %

Iperf Test Results:5 CPU bound Domains

1 Mixed workload Domain

Number of runs

Mbits/s

DOM3 Web Server

DOM2DOM1

DOM4 DOM5

DOM3Database

Server

DOM2DOM1

DOM4 DOM5

Scenario: Interaction between Web server and DB server.

Realistic Workload Test:

Realistic Workload Test:

Credit SchedulerTotal time: 605 secAvg time per query: 6022ms

UtopiaTotal time: 8.5965 secAvg time per query:85.93ms

Improvement : 6943 %

0.0-2.0 2.0-4.0 4.0-6.0 6.0-8.0 8.0-10.0

10.0-12.0

12.0-14.0

14.0-16.0

16.0-18.0

18.0-20.0

20.0-22.0

22.0-24.0

24.0-26.0

26.0-28.0

28.0-30.0

100

200

300

400

500

600

700

800

Relative weight 1Relative weight 0.25

Mbits/s

Seconds

Performance Isolation.Iperf Benchmark

Side effects:• 9% decrease in CPU throughput.

• 13% decrease in throughput of I/O bound VM.

Credit Scheduler Utopia0

2

4

6

8

10

12

14

16 15.2

13.1

1.39

9.21

I/O boundMixed bound

Utopia Credit Scheduler300000

320000

340000

360000

380000

400000

420000

388407.78

398513.525

Dhrystone2 - lps

Dhrystone2 CPU benchmark test Iperf test. 4 CPU bound doms, 1 I/O bound and 1 mixed workload Dom

Future Work

• Optimization for multi-core processors

• Dynamically assigning IDD credits, based on the changing behavior of VMs.

QUESTIONS?

THANK YOU