I am a Postdoctoral Researcher at the Department of Computer Science and Engineering at the University of Ioannina in Greece.
I am Giorgos E. Kappes from Ioannina, Greece and, currently,
I am a Postdoctoral Researcher at the Computer Systems Lab (CSL)
of the University of Ioannina.
I have extensive experience
in conducting research in Computer Systems. My research includes the design, development, and
evaluation of system software for multi-tenant cloud environments. My research interests
include operating systems, data storage, and systems security. I am also an expert in deployment
and administration of enterprise-level IT infrastructure with over eight years of hands-on experience.
I hold a PhD in Computer Science, an MSc in Computer Systems, and a BSc degree from the
Department of Computer Science and Engineering,
I completed my PhD and MSc under the supervision of
Prof. Stergios Anastasiadis.
In our research we studied approaches for efficient, effective, and secure support of multitenancy in
the datacenters of modern cloud environments.
For more information about me, you can
find my short resume in English, or my extensive
corriculum vitae in Greek, and
English.
You can also check my
github, and
gitlab profiles for a list of open source
projects that I've contributed on.
My main research interests lie in the fields of operating systems, data storage, and systems security. However, I am interested in pretty much everything to do with computer systems. Following are some of the projects that I have worked on:
User-level Services for Multitenant Isolation.
The focus of this project is to enable multiple tenants to efficiently and
securely share the computing, storage, and network infrastructure of the datacenter and
reduce the conention for shared resources.
To this end, we take the radical approach of moving the data-intensive I/O
services at user level from the shared kernel, in order to serve the containers of
competing tenants over the same cloud machines. Our contributions consist of innovative
methods to handle POSIX-like system calls at user level through a library, the
producer-consumer transfer of data and requests over shared memory with efficient memory
copy and relaxed lock-free queues, the construction of stacked user-level I/O services,
and a multitenant access control mechanism built natively into a distributed filesystem.
Relaxed Concurrent Queues. The producer-consumer communication over shared memory is a critical function of current scalable systems. Queues that provide low latency and high throughput on highly utilized systems can improve the overall performance perceived by the end users. In order to address this demand, we set as priority to achieve both high operation performance and item transfer speed. The Relaxed Concurrent Queues (RCQs) are a family of queues that we have designed and implemented for that purpose. Our key idea is a relaxed ordering model that splits the enqueue and dequeue operations into a stage of sequential assignment to a queue slot and a stage of concurrent execution across the slots. At each slot, we apply no order restrictions among the operations of the same type. We experimentally show that our algorithms achieve factors to orders of magnitude advantage over the state-of-the-art strict or relaxed queue algorithms.
Optimized memory copy. Critical operations are often implemented in roughly the same way across multiple platforms, but differently by software systems running on the same platform. This observation is arguably justified by the potential restrictions of each software system, but it is surprising given the operation sensitivity to numerous platform-specific software and hardware parameters. With initial focus on the memory copy operation (memcpy), we introduce a methodology based on exhaustive search to optimize the performance across different platforms. We design and implement the Asterope algorithm to experimentally generate optimal memcpy parameters for two x86-64 processor models from different vendors. With experiments on microbenchmarks and two production systems, we demonstrate that Asterope respectively achieves up to 2.4x and 1.9x higher function and system performance in comparison to using the Linux kernel memcpy.
Multitenant Access Control.
Secure access control is a challenging problem that organizations face in
collaborative virtual environments, which has prevented many of them from migrating
critical data or applications into these environments. In our research we examined
approaches for efficient and effective support of multitenancy in filesystems used
in cloud environments. We introduced a system architecture that is backwards compatible to
object-based filesystems, and combines native access control with namespace isolation.
Our architecture securely isolates dfferent tenants, and enables flexible file sharing both
within and among tenants. We developed a Linux-based prototype solution over Ceph and
obtained encouraging experimental results about the scalability and low overhead of
our design on a local cluster and on Amazon AWS.
Most likely you will find me at A34 office in the first floor of the department. If not, below is more information on how you can reach me.
I use GnuPG for email encryption and signing. I also use it
to sign digital content that I create (such as code, documents, and my web pages).
The ID of my personal GPG key is 0xD614E92E88507AE1. You can find the key on the
SKS OpenPGP Public Key server
and here:
pubring,
public key,
fingerprint.
In case you would like to send me a confidential email, please use my key to secure it.
Additionally, please sign the email with your signing key and provide me with your public key, so that I
can verify your signature.