Paolo Valente

Assistant Professor of Computer Science Dipartimento di Ingegneria dell'Informazione Università di Modena e Reggio Emilia Via Vignolese 905/b - 41100 Modena (Italy) tel: +39 059 2056318 - fax: +39 059 2056129 paolo dot valente at unimore dot it and Istituto di Informatica e Telematica Consiglio Nazionale delle Ricerche Via Moruzzi 1 56124 Pisa (Italy)

About myself...

I was born on the 10th Semptember, 1973 in Cassino (FR). I graduated (cum laude) in Computer Engineering at University of Pisa on October 2000 with a graduation thesis developed at the Information Engineering Department of the University of Pisa on the development of a packet Fair Queueing algorithm for the FreeBSD kernel.
I worked at the at the Information Engineering Department of the University of Pisa as a PhD student from 2001 to the end of 2004. I received my PhD on May 2005, with a thesis on scheduling algorithms for QoS provisioning.
Starting from Sptember 2006, I am an Assistant professor (Ricercatore) at the Department of Computer Science of the University of Modena.
So far my research activity has been mainly focused on CPU, network and disk scheduling algorithms for QoS provisioning. Especially, I have been recently working on Multiprocessor scheduling. Since the early months of 2007 I also began working on Bioinformatics algorithms (motif search).

Publications

(and related news)

• P. Valente, F. Checconi, “High Throughput Disk Scheduling with Deterministic Guarantees on Bandwidth Distribution”, draft , to appear on IEEE Transactions on Computers.

This draft is about BFQ, a new disk scheduler I'm currently working on with Fabio Checconi. We implemented it for several Linux kernel releases, from 2.6.21 to 2.6.28-rc4 (upon the last update to this page). The first proposal received a good feedback (article on kerneltrap). We submitted an extended version on Nov 11 2008.

One of the nice properties of BFQ is that, differently from all the research schedulers we are aware of (including the below-mentioned Hybrid scheduler), it preserves service guarantees also in presence of synchronous requests.

You can find here all the stuff related to BFQ (patches, experimental results, programs used for the experiments and so on).

• M. Leoncini, P. Santi, P. Valente, “An STDMA-based framework for QoS provisioning in wireless mesh networks”, Proceedings of IEEE MASS 2008, October 2008.
Click here to download an extended version of this paper.


• P. Valente, “Exact GPS simulation with logarithmic complexity, and its application to an optimally fair scheduler”, Proceedings of SIGCOMM’04, pages 269-280, August 2004.

Some bugs have been fixed in the (pseudo-)code of both L-GPS and L-WF2Q. The most important ones have been found and fixed by Ming-I Hsieh. A hopefully bug-free version of the algorithms can be found in the following journal version of the paper.



• P. Valente, “Exact GPS simulation with logarithmic complexity, and its application to an optimally fair scheduler“, IEEE/ACM Transactions on Networking (ToN), February 2008.
  
  Extended and improved version of my SIGCOMM paper about L-GPS and L-WF2Q. Click here to download the new paper.



• L. Rizzo, P. Valente, “Hybrid: achieving deterministic fairness and high throughput in disk scheduling”, Proceedings of CCCT’04, August 2004.
  
  Hybrid has been also implemented by Luigi Rizzo and Emiliano Mennucci in the project "Pluggable disk scheduler for FreeBSD", which has been selected for funding from the Google "Summer of  Code" program :-)
  While implementing Hybrid on Linux and working on an improved version of the paper with Fabio Checconi, we bumped into the loss of the expected guarantees in case of synchronous disk requests. Unfortunately, the same problem is shared by all the disk schedulers we read about in the literature. To preserve service guarantees and to get a high throughput also in presence of synchrnous requests we defined the above mentioned BFQ scheduler.
  
  
  
• P. Valente, "Extending WF2Q+ to support a dynamic traffic mix", Proceedings of AAA-IDEA'05, June 2005.
  
  An updated version of the paper is available: with respect to the previous version, it contains some considerations about constraining or not constraining the maximum value of the sum of the weights of the flows.
  
  You can find an implementation of Time-driven Removal (TdR) -- the simple extension for WF2Q+ defined in the paper -- inside the code of Hybrid, developed in the above mentioned "Pluggable disk scheduler for FreeBSD" project.
  
  
  
• Paolo Valente, Giuseppe Lipari, "An Upper Bound to the Lateness of Soft Real-time Tasks Scheduled by EDF on Multiprocessors", Proceedings of RTSS'05, December 2005.
  
  A bug has been found in one of the proofs (credits: UmaMaheswari C. Devi).
  
  We prepared a backup Technical Report, containing only a subset of the sane proofs of the published paper. The proofs used in this TR leads to a higher bound with respect to the published paper.
  
  We are also working on a new Technical Report containing a slightly different set of proofs, which should not be affected by that error. Contact me for details.
  
  Finally, you can click here to download an extended version of the original paper highlighting the point where the bug is.
  
  


• Luigi Palopoli, Tommaso Cucinotta, Luca Marzario, Antonio Mancina, Paolo Valente, "A unified framework for managing different resources with QoS guarantees", Proceedings of OSPERT'05, July 2005.
  
  
  
• M. Federico, P. Valente, M. Leoncini, M. Montangero, R. Cavicchioli, "An Efficient Algorithm for Planted Structured Motif Extraction", Proc. Int. Workshop COMPBIO '09, Breaking Frontiers of Computational Biology, May 2009.

Teaching

• Computer Programming I course (in Italian), held in the Laurea in Informatica degree at the Faculty of Scienze Matematiche, Fisiche e Naturali, Modena