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std::bodun::blog

PhD @ UT Austin. OS, network, heterogeneity, anything system.

Linux Program Measurement and mmap

Sep 23, 2020
This is a summary over Linux kernel program measurement and mmap. The specs of our experiment environment is listed below. For more details regarding the CPU spec please refer to cpu world for more info...

Memory Resource Management in VMware ESX Server

Sep 21, 2020
VMWare ESX Server is a software layer designed to multiplex hardware resources among virtual machines running unmodified commodity operating systems. ESX Server, different to VMware Workstation , is a type 1 hypervisor, which means it runs directly on bare metal. ESX Server focuses on running guest VMs without modifying the guest OSes at all, which is challenging. Memory Virtualization is done by interposing an extra abstraction layer between a physical address from the VM’s point of view, and a machine address which represents the actual hardware memory....

Xen and the Art of Virtualization

Sep 16, 2020
Xen is an x86 virtual machine monitor which allows multiple commodity operating systems to share conventional hardware in a safe and resource managed fashion, without sacrificing either performance or functionality. Xen is type I hypervisor, which directly runs on top of bare metal. We will summarize what Xen is what its attributes are. paravirtualization - presents a virtual machine abstraction that is similar but not identical to the underlying hardware....

Start Linux Kernel Hacking

Sep 14, 2020
This is a summary of how to compile and boot the Linux kernel on the KVM-qemu virtual machine. It covers how to get a VM running in KVM, how to build a customized kernel, and how to use GDB with the Linux kernel. The experiment is conducted on an amd64 architecture CPU. We use Ubuntu as our testing environment but the steps covered here should apply to other distros as well...

Performance Anomaly of 802.11b

Sep 13, 2020
This research is conducted by Martin Heusse, Franck Rousseau, Cilles Berger-Sabbatel, Andrzej Duda on analyzing the performance of the IEEE 802.11b wireless local area networks. Degraded transmitting rate is caused by CSMA/CA channel access method...

Exokernel

Sep 1, 2020
Exokernel is a term every system researcher has heard of at some point in life. However, according to the PDOS group at MIT, there aren’t any exokernel-based operating systems in active use today. It’s interesting to discover what ideas exokernels brought to the OS high-level design and some potential drawbacks of such design choice...

Sketch on the UNIX Timesharing System

Aug 27, 2020
Unix is general-purpose, multi-user, interactive operating system, it offers several new features hardly found in other larger operating systems back in the day. These features include (1) a hierarchical file system incorporating demountable volumes; (2) compatible file, device, and inter-process I/O; (3) the ability to initiate asynchronous processes; (4) system command language selectable on a per-user basis; and (5) over 100 subsystems including a dozen languages...

Monads in Haskell

Mar 1, 2020
I’ve scratched my head for quite a while trying to understand the concept of monad in Haskell. This is a brief summary of monads. I take William Cook’s Anatomy of Programming Languages as my reference...

Singular Value Decomposition

Feb 10, 2020
Unitary matrices and the Singular Value Decomposition (SVD) are two important concepts in linear algebra. In order to fully understand these concepts, we will need to first discuss orthogonality. Most materials are converted in Advanced Linear Algebra: Foundations to Frontiers taught by professor Robert van de Geijn . This is a brief summary over the important concepts covered in Chapter 2...

Understanding Probabilistic Clock Synchronization

Sep 17, 2019
This post is meant to discuss the probabilistic clock synchronization technique. The main goal of this technique is to bound the difference between systems by setting up an upper bound. Formally, we define the problem as \(|P(t)-Q(t)|\leq \varepsilon\), or the difference between clocks across the network. We will go over the technical detains and discuss what these symbols represent in later sections. Most of these materials are from Prof. Mok ’s slides on his dependable systems classes....