Dynamic Soft Real Time CPU Scheduler 2.0
This is the dynamic soft real time scheduler by the Monet
at the Department of Computer
Science, University of Illinois at Urbana-Champaign.
This release has been tested on SunOS 5.7, SGI IRIX 6.5, Linux(RedHat 6.2)
, and Windows NT.
* General Description
* Software :
DSRT CPU Scheduler,
CPU Monitor, and
* DSRT 2.0 under Windows NT
* DSRT 2.0 under Linux
* DSRT Monitoring
* Coordinating Power-Aware Adaptation of Applications and Hardware Resources
* DSRT Multi-Processor for Win2K
* Ongoing work
* Related Sites
* Mpeg Clips
Multimedia applications such as video/audio processing, animation are
time-sensitive because these applications need minimal jitter to accomplish
a good viewing quality. They require that underlying systems support
sufficient and constant processing time so that they can provide
Quality of Service(QoS) guarantees to the users in terms of minimum
throughput, maximum response time and CPU cycles. However, in current
time-sharing environments, these multimedia applications do not perform
well when they are scheduled concurrently with the traditional nonreal-time
applications. On the other hand, allowing enough CPU to real-time
applications may cause nonreal-time applications to use unfair CPU bandwidth.
DSRT scheduler targets fair CPU distribution among competent applications
as well as guarantee of time constraints of real-time applications.
Another issue is that process scheduling has beed discussed inside OS kernel
level. So in order to get new scheduling scinario, kernel source code is
required to be modified and re-installed. DSRT scheduler is designed
as a middleware scheduler and thus it can be used by copying executable
scheduler into the target machine withoug modifying underlying kernel.
The dynamic soft real time scheduler (DSRT) 2.0 is a user-level dynamic
scheduler that can schedule soft real time (RT) periodic and aperiodic
tasks. The DSRT 2.0 contains the following features
CPU service classes. A RT process first enters a reservation with
the DSRT scheduler before its actual real time execution. The reservation
describes the processor usage pattern of the RT process during its real
time execution. Depending on the type of the applications, their
processor usage pattern may be constant, variable, periodic, or aperiodic.
The DSRT scheduler provides various classes of reservation:
Periodic constant processing time class.
Periodic constrained constant processing time class.
Periodic variable processing time class.
Aperiodic constant processing time class.
Guarantee time sharing (TS) allocation. The TS process will receive
a minimum fixed percentage of processor bandwidth so that they will not
be starved in the presence of RT processes.
Overrun protection. This means that if a misbehaving RT process (e.g,
using more processor time than it has reserved) cannot adversely affect
the guarantees that the scheduler made to other behaving RT processes.
System-initiated adaptation. The RT process can specify an adaptation
strategy for the DSRT scheduler to automatically adjust the reservation
based on the actual usage pattern of the RT process. The DSRT scheduler
provides the following adaptation strategies:
range [min, max] adaptation.
exponential average adaptation.
Smart probing. Probing allows the RT application to get an accurate
estimation on the reservation parameters, e.g. service class, or percentage
of processor utilization.
Reservation re-negotiation. The RT process can modify the reservation
Scheduler monitor. The scheduler monitor provides various information
on the RT processes including their usage, overrun, and deadline misses
Allocation algorithm/policy for process overruns.
The DSRT 2.0 scheduler has the following improvements over the previously
released DSRT 1.0:
CPU service classes.
Smart probing: automatic selection of CPU service class and reservation
Fix various security loopholes.
More monitoring data on the real time processes and the CPU scheduler.
Currently we are taking two different approaches; adding more functionalities
on DSRT scheduler and porting DSRT scheduler into Window NT and Linux based
The added features will be as follows.
- A new CPU service class for sporadic tasks
- CPU broker for CPU brokerage services : scheduler consists of two components
(CPU broker and dispatcher)
- Advance reservation handling : reservation of CPU bandwidth is made for future use
- User-level thread scheduler
- Hao-hua Chu (Ph.D Graduate, June 1999)
- Lintian Qiao (Ph.D Graduate)
- Roland Geisler (M.S Graduate, June 1999)
- Goutham Garimella (M.S Graduate, June 1999)
- Manish Gupta (M.S Graduate, June 1999)
- Arun Viswanathan (M.S Graduate, June 2000)
- Priti Goel (M.S Graduate, June 2000)
- Kihun Kim (M.S Graduate, August 2001)
- Diwakar Gupta (M.S Graduate, May 2002)
- Jim Jackson (M.S Graduate, May 2002)
- W. Yuan, K. Nahrstedt, S. Adve, D. Jones, and R. Kravets, GRACE: Cross-Layer Adaptation for Multimedia Quality and Battery Energy, To appear in IEEE Transaction on Mobile Computing.
- Wanghong Yuan and Klara Nahrstedt, Practical Voltage Scaling for Mobile Multimedia Devices, in Proc. of ACM Multimedia 2004, New York, NY, October, 2004. pdf
- Wanghong Yuan and Klara Nahrstedt, Process Group Management in Cross-Layer Adaptation, in Proc. of SPIE/ACM Multimedia Computing and Networking Conference (MMCN'04), Santa Clara, CA, January, 2004. pdf
- Wanghong Yuan and Klara Nahrstedt, Energy-Efficient Soft Real-Time CPU Scheduling for Mobile Multimedia Systems, in Proc. of 19th ACM Symposium on Operating Systems Principles (SOSP'03), Bolton Landing, NY, October, 2003. pdf
- Wanghong Yuan and Klara Nahrstedt, Buffering Approach for Energy Saving in Video Sensors, in Proc. of IEEE International Conference on Multimedia and Expo (ICME2003), Baltimore, MD, July, 2003. pdf
- Wanghong Yuan and Klara Nahrstedt, ReCalendar: Calendaring and Scheduling Applications with CPU and Energy Resource Guarantees for Mobile Devices, in Proc. of IEEE International Conference on Pervasive Computing and Communications (PerCom 2003), Dallas-Fort Worth, Texas, March, 2003. pdf
- W. Yuan, K. Nahrstedt, S. Adve, D. Jones, and R. Kravets, Design and Evaluation of A Cross-Layer Adaptation Framework for Mobile Multimedia Systems, in Proc. of SPIE/ACM Multimedia Computing and Networking Conference (MMCN'03), Santa Clara, CA, January, 2003. pdf
- S. Adve, A. Harris, C. Hughes, D. Jones, R. Kravets, K. Nahrstedt, D. Sachs, R. Sasanka, J. Srinivasan, W. Yuan, The Illinois GRACE Project: Global Resource Adaptation through CoopEration, in Proc. of Workshop on Self-Healing, Adaptive and self-MANaged Systems (SHAMAN02), New York City, NY, June, 2002. ps
- Wanghong Yuan and Klara Nahrstedt, Integration of Dynamic Voltage Scaling and Soft Real-Time Scheduling for Open Mobile Systems, in Proc. of 12th International Workshop on Network and Operating Systems Support for Digital Audio and Video (NOSSDAV '02), pp. 105-114, Miami Beach, Florida, May, 2002. pdf
- Wanghong Yuan and Klara Nahrstedt, A Middleware Framework Coordinating Processor/Power Resource Management for Multimedia Applications, in Proc. of IEEE Globecom 2001, San Antonio, Texas, November, 2001. pdf
- Wanghong Yuan, Klara Nahrstedt and Xiaohui Gu, Coordinating Energy-Aware Adaptation of Multimedia Applications and Hardware, in Proc. of 9th ACM Multimedia (Multimedia Middleware Workshop), Ottawa, Canada, October, 2001. ps
- Wanghong Yuan, Klara Nahrstedt, Kihun Kim, R-EDF: A Reservation-Based EDF Scheduling Algorithm for Multiple Multimedia Task Classes, in Proc. of 7th IEEE Real-Time Technology and Applications Symposium, Taipei, Taiwan, May, 2001. ps
Hao-hua Chu, Klara Nahrstedt, CPU
Service Classes for Multimedia Applications, to appear in Proceedings
of IEEE International Conference on Multimedia Computing and Systems
(IEEE Multimedia Systems '99), Florence, Italy, June 7-11, 1999.
Hao-Hua Chu, Klara Nahrstedt: A Soft Real Time Scheduling Server in UNIX
Operating System. IDMS 1997: 153-162
Hao-hua Chu, Klara Nahrstedt, Jiang Qian. Dynamic Soft Real Time
Scheduling Framework for Multimedia Environment,
submitted to IEEE Real-Time Systems Symposium, December 1999.
Wanghong Yuan, GRACE-OS: An Energy-Efficient Mobile Multimedia Operating System, Ph.D. Thesis, Department of Computer Science, University of Illinois at Urbana-Champaign, October, 2004. pdf
Kihun Kim, Extended DSRT System,
Department of Computer Science, University of Illinois at
Urbana-Champaign, August 2000.
This research is funded by the Air Force grant F30602-97-2-0121, the NSF
CCR 96-23867, the NSF PACI grant ACU-96-19019, and in part the NSF CISE
Any opinions, findings, and conclusions or recommendations expressed in
this material are those of the author(s) and do not necessarily reflect the
views of the funding agencies. If you have questions or comments, send email to
Copyright (©) 1997-2000, Multimedia Operating Systems and Networking Group,
University of Illinois at Urbana-Champaign
Phone: (217)333-1515 (USA)
Updated at October 10, 2000