Category: Data Structures
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RioVista – Summary and notes
Introduction Key Words: ACID, transactions, synchronous I/O RioVista picks up where LRVM left off and aims for a performance conscience transaction. In other words, how can RioVista reduce the overhead of synchronous I/O, attracting system designers to use transactions System Crash Key Words: power crash, software crash, UPS power supply Super interesting concept that makes…
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Lightweight recoverable virtual machine – Summary and Notes
Summary and main take away As system designers, we can make persistence into the virtual memory manager, offering persistence to application developers. However, it’s no easy feat: we need to ensure that the solution performs well. To this end, the virtual machine manager offers an API that allows developer to wrap their code in transactions;…
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Distributed File Systems – Summary and notes
This lesson introduces network file system (NFS) and presents the problems with it, bottlenecks including limited cache and expensive input/output (I/O) operations. These problems motivate the need for a distributed file system, in which there is no longer a centralized server. Instead, there are multiple clients and servers that play various roles including serving data…
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Distributed Shared Memory (Part 2 of 2) Notes
An example Summary Key Words: Conditional variable, pthread_signal, pthread_wait in the concrete example (screenshot below), P1 instructions that update memory (e.g. flag = 1) can be run in parallel with that of P2 because of release consistency model Advantage of RC over SC Summary In a nutshell, we gain performance in a shared memory…
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What I learned from writing synchronization barriers
Before starting project 2 (for my advanced operating systems course), I took a snapshot of my understanding of synchronization barriers. In retrospect, I’m glad I took 10 minutes out of my day to jot down what I did (and did not) know because now, I get a clearer pictur eof what I learned. Overall, I…
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What’s the point of the parity flag in the dissemination barrier?
I’m implementating the dissemination barrier (above) in C for my advanced OS course and I’m not quite sure I understand the pseudo code itself. In particular, I don’t get the point of the parity flag …. what’s the point of it? What problem does it solve? Isn’t the localsense variable sufficient to detect whether or…
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OpenMP tutorial notes (Part 1)
I’m watching the YouTube learning series called “Introduction to OpenMP” in order to get a better understanding of how I can use the framework for my second project in advanced operating systems. You might find the below notes useful if you don’t want to sit through the entire video series. Introduction to OpenMP: 02 part…
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Barrier Synchronization (Part 2/2)
Part 1 of barrier synchronization covers my notes on the first couple types of synchronization barriers including the naive centralized barrier and the slightly more advanced tree barrier. This post is a continuation and covers the three other barriers: MCS barrier, tournament barrier , dissemination barrier. Summary In the MCS tree barrier, there are two…
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Finally clean air & Daily Review – Day ending in 2020/09/18
Hooray! Today is the first day in a couple weeks that air quality is considered good, at least according to the EPA. I’m so pleased and so grateful for clean air because my wife and daughter have not left the house since the wild fires started a week ago (or was it two weeks —…
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Barrier Synchronization (Part 1/2)
As mentioned previously, there are different types of synchronization primitives that us operating system designers offer. If as an application designer you nee to ensure only one thread can access a piece of shared memory at a time, use a mutual exclusion synchronization primitive. But what about a different scenario in which you need all…
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On letting go & Daily Review – Day ending in 2020/09/17
With working remote and establishing a (somewhat) daily routine (that has become pretty monotonous), it’s sometimes easy to forget that we’re in the midst of a global pandemic. But that reality is amplified because of the recent wild fires, forcing those of us living in the pacific north west (PNW) — and those living in…
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Making sense of the “sense reversing barrier” (synchronization)
What’s the deal with a sense reversing barrier? Even after watching the lectures on the topic, I was still confused as to how a single flag could toggle between two values (true and false) can communicate whether or not all processes (or threads) are running in the same critical section. This concept completely baffled me.…
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Crashing and burning during lunch & Daily Review – Day ending in 2020/09/16
I had mentioned yesterday that I slept horribly, waking up early and starting day off at around 03:45 AM. That wake up time was brutal and as a result, I crashed and burned in the afternoon, leveraging those precious 30 minutes of my lunch to nap in my wife’s / daughter’s bedroom (a room with…
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Synchronization notes (part 2/2) – Linked Based Queuing lock
In part 1 of synchronization, I talked about the more naive spin locks and other naive approaches that offer only marginally better performance by adding delays or reading cached caches (i.e. avoiding bus traffic) and so on. Of all the locks discussed thus far, the array based queuing lock offers low latency, low contention and…
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Tired like a zombie & Daily Review – Day ending in 2020/09/15
Today is going to be rough. I slept horribly, waking up multiple times throughout the night. Ultimately, I rolled out of my tri-folding foam mattress (a temporary bed while my daughter and wife sleep on the mattress in a separate room as to not wake me up: that parent life) at 03:45 AM this morning.…
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Synchronization (Notes) – Part 1
I broke down the synchronization topic into two parts and this will cover material up to and including the array based queuing lock. I’ll follow up with part 2 tomorrow, which will include the linked list based queuing lock. There a couple different types of synchronization primitives: mutual exclusion and barrier synchronization. Mutual exclusion ensures…
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Honoring my body’s internal alarm clock & Daily Review – Day ending in 2020/09/14
This morning my body woke me up later than usual. After a few blinks, I squeezed the corner of my Casio G-Shock watch, the green background lighting up and shining the time: 05:55 AM. Ugh. About an hour later than I wanted to wake up. On one hand, I’m bummed because I won’t be able…
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Memory Virtualization (notes)
The operating system maintains a per process data structure called a page table, creating a protection domain and hardware address space: another virtualization technique. This page table maps the virtual address space to physical frame number (PFN). The same virtualization technique is adopted by hypervisors (e.g. VMWare). They too have the responsibility of mapping the…
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Papers to read for designing and writing up the C memory coordinator
Below are some memory management research papers that my classmate shared with the rest of us on Piazza1. Quickly scanning over the papers, I think the material will point me in the right direction and will paint a clearer picture of how I might want to approach writing my memory coordinator. I do wonder if…
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A snapshot of my understanding before tackling the memory coordinator
Now that I finished writing the vCPU scheduler for project 1, I’m moving on to the second part of the project called the “memory coordinator” and here I’m posting a similar blog post to a snapshot of my understanding of project 1 , the motivation being that I take for granted what I learned throughout…
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A snapshot of my understanding before beginning project 1 (scheduler, memory coordinator)
Project 1 was released last evening at 08:59 PM PST and this morning, I decided to start on the project by reading through the overview and get the lay of the land. For this project, we’ll need to deliver to operating system components: a scheduler and a memory coordinator (not even sure what that means…