Blog posts
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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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Shared Memory Machine Model (notes)
You need to take away the following two themes for shared memory machine model: Difference and relationship between cache coherence (dealt with in hardware) and cache consistency (handled by the operating system) The different memory machine models (e.g. dance hall, symmetric multiprocessing, and distributed shared memory architecture) Cache coherence is the promise delivered by the…
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Losing 2 hours searching for a website bookmark & Weekly Review: week ending in 2020/09/06
My weekly review that normally takes place first thing in the morning on Sundays was completely derailed this time around, all because I could find the URL to a website that I had sworn I bookmarked for my wife’s birthday present. I ended up coughing up two hours of searching: searching directly on Reddit’s website…
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Remembering September 11 & Daily Review (day ending on 09/11/2020)
Yesterday was September 11. On this day, every year, Americans grieve and we are all reminded of the unforgettable day back in 2001 when the New York twin towers collapsed to the ground after being struck by the hijacked planes. I sure remember the day. I was about 12 years old at the time and…
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CPU and Device Virtualization (notes)
This post is a continuation of virtualization. In the previous post, I talked about memory virtualization. This post instead discusses CPU and device virtualization. Ultimately, as system designers, one of our chief aims is to provide an illusion to the underlying guest operating systems that they each individually won the underlying hardware, the CPU and…
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Memory coordinator test cases (and expected outcome)
I’m getting ready to begin developing a memory coordinator for project 1 but before I write a single line of (C) code, I want to run the provided test cases and read the output of the tests so that a get a better grip of the memory coordinator’s actual objective. I’ll refer back to these…
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Daily Review – Day ending in 2020/09/10
We often talk about work life balance, separating the two major parts of our lives. On some level, I agree with the philosophy, believe that work is work and life is life. But at least for me, what happens at work bleeds into my personal life, and vice versa. When I have a shitty day…
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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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Daily Review – Day ending in 2020/09/09
After freeing a spider into the front yard, I noticed that the coffee mug (in which I trapped the spider in) was decorated with a beautiful web that the spider must’ve spun overnight. Almost every other day, I spot a spider dancing across the white walls of my bedroom. Instead of squishing them to death…
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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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How to obtain the length of the memory statistics array when calling virDomainMemoryStats
Up to ‘nr_stats’ elements of ‘stats’ will be populated with memory statistics from the domain. Only statistics supported by the domain, the driver, and this version of libvirt will be returned. What does the above API description even mean by nr_stats? How do you determine the number of elements that need to be populated? For…
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Daily Review – Day ending in 2020/09/08
The most interesting side effect of writing these daily reviews is that they stir up meaningful conversations with my wife. Apparently, much of what words I set on paper never make their way out of my mouth (despite thinking that I did verbally share them). Surely this situation of my brain tricking me into thinking…
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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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Quotes from “My life story” by Veritasium
During some down time this evening, I watched the below YouTube video clip filmed and produced by Veritasium and I absolutely loved hearing about his journey, especially about how becoming a father has fundamentally changed the way he views his time. Because I’m in a similar boat: My life looks nothing like it did a…
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Introduction to virtualization (notes)
As system designers, our goal is to design a “black box” system that create an illusion that our users have full and independent access to the underlying hardware of the system. This is merely an abstraction since we are building multi-tenant systems with many applications and many virtual guest machines running on a single piece…
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Daily Review – Day ending in 2020/09/07
Yesterday Writing Blogged and published an entry describing my naive scheduler for project 1 Emotions I disassociated and my mind wandered into its “own world” after my wife Jess asked me to watch Elliott later that afternoon. I think part of the reason why I got so worked up had less to do with her…
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A naive round robin CPU scheduler
A couple days ago, I spent maybe an hour whipping together a vary naive CPU scheduler for project 1 in advanced operating systems. This naive scheduler pins each of the virtual CPUs in a round robin fashion, not taking utilization (or any other factor) into consideration. For example, say we have four virtual CPUs and…
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Distancing oneself from a difficult problem
I fixed a silly bug just now and wrote working code that can pin multiple virtual CPUs to the physical CPUs. Identifying the bug in my code was another classic example of how I needed to distance myself from the problem. Instead of staying up late into the night (late is now 09:30 pm on…
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Weekly Review – Week ending in 2020/09/06
Writing I’m getting much more comfortable with publishing blog posts that are not completely polished. The fear of letting the world see less my less the perfect propose is utter non-sense. In fact, writing and publishing frequently offers two benefits. The first is that the sheer act of writing and setting words on (digital) paper…
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Advanced Operating Systems (Project 1) – monitoring CPU affinity before launching my own scheduler
Project 1 requires that we write a CPU scheduler and memory coordinator. Right now, I’m focusing my attention on the former and the objective for this part of the project is write some C code that pins virtual CPUs to physical CPUs based off of the utilization statistics gathered with the libvrt library (I was…