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Profiling Go
Techniques and tools for profiling Go applications including pprof, benchmarks, and memory management analysis.
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A deep dive into Multicore OCaml garbage collector
I recently gave a talk on the internals of multicore OCaml GC at Jane Street offices in NYC. The slides from the talk are available online . But I felt that the slides alone aren’t particularly edifying. This post is basically the slides from the talk annotated with notes.
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Why is memory reclamation so important for lock-free algorithms?
As it so happens, object lifetime tracking (or Memory Reclamation as I prefer to call it) is the current most difficult open problem in sha...
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Finding the Lost Vikings – Reversing a Virtual Machine
After having fun reverse engineering the Comprehend Adventure game (Recomprehend) I was looking for a new DOS game reverse engineering project. Over the years various people have reversed a lot of …
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How should you build a high-performance column store for the 2020s?
Though most relational databases (like MySQL) are "row oriented", in that they keep rows stored together... experience has taught us that pivoting the data arrow so that columns, and not rows, are stored together can be beneficial. This is an old observation that most experienced programmers know about as the…
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Delete an inline function, save 794 kB
In the previous episode of “Simple Changes to Shrink Chrome” I discussed how deleting ‘const’ from a few key locations could lead to dramatic size savings, due to a VC++ com…
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FreeBSD/EC2 on C5 instances
Ever since the first EC2 instances launched — the ones which were retrospectively named "m1.small" — Amazon has relied on the Xen hypervisor. No longer: C5 instances use KVM. This sounds like it would be a problem, but in fact that change didn't bother FreeBSD at all: Now that everything uses hardware-based paging…
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Why isn't memset() async-signal-safe?
Really, POSIX? Really? memset() isn't async-signal-safe? How is it not safe? … oh … that's why
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A Deep Dive into HandBrake and Video Transcoding
An obvious interest area of mine is in ripping (and watching) movies using my Mac. I've talked about everything from installing the tools I use to how I rip to how to make sure I update the ripping tools . And though I've included some comparison pictures in the how-I-rip article, I've never done a deep dive into the…
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Debugging macOS Kernel Using VirtualBox
Update: In the HN discussion, awalton mentioned you can set CPUID flags in VMWare. Simply adding cpuid.7.ebx = "-----------0--------------------" to the vmx file will disable SMAP. Late last year, I upgraded my old MBP to the 2016 model with a Skylake processor. As I was debugging a kernel exploit, it turned out that…
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Epoll is fundamentally broken
This time we'll focus on Linux's select(2) successor - the epoll(2) I/O multiplexing syscall.
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Software architecture is failing
I doubt there has ever been a time when software architecture was seen as a raging success. The “three-tier architecture” of the web has held up extremely well and is an excellent place for many people to start. The “12 Factor App” approach has encouraged developers to adopt practices that make deployment and scaling…
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Filesystem error handling
We’re going to reproduce some results from papers on filesystem robustness that were written up roughly a decade ago : Prabhakaran et al. SOSP 05 paper , which injected errors below the filesystem and Gunawi et al. FAST 08 , which looked at how often filesystems failed to check return codes of functions that can…
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OpenBSD and the modern laptop
Did you think that OpenBSD is suitable only for firewalls and high-security servers? Think again. Here are my steps to transform a modern m...
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On Disk IO, Part 3: LSM Trees
If you like the series, check out my book on Database Internals!
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Linux Bridge – How it works
developer. curious. learner
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Mosaic: processing a trillion-edge graph on a single machine
Mosaic: Processing a trillion-edge graph on a single machine Maass et al., EuroSys’17 Unless your graph is bigger than Facebook’s, you can process it on a single machine. With the incep…
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AWS EC2 Virtualization 2017: Including Nitro
AWS EC2 Virtualization 2017: explaining the different virtualization types, from emulation and binary substitution, paravirtualization and Xen, PV, HVM, and PVHVM modes, and the new Nitro hypervisor
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Debian port for RISC-V 64-bit
This is a post describing my involvement with the Debian GNU/Linux port for RISC-V (unofficial and not endorsed by Debian at the moment) and announcing the availability of the repository (still very much WIP) with packages built for this architecture. If not interested in the story but you want to check the…
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What is Windows doing while hogging that lock?
Earlier this month I wrote about how Windows 10 holds a lock during too much of process destruction, which both serializes this task and causes mouse-cursor hitches and UI hangs (because the same l…
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Event-Driven Architecture
Using events to design applications is a practice that seems to be around since the late 1980s. We can use events anywhere in the frontend or backend. When a button is pressed, when some data chang…
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Preventing server overload: limit requests being processed
Recently at Bluecore I ran into a familiar situation: during brief periods of overload, all requests to a server were timing out. It was a catastrophic failure, where the server completely stopped serving. We added more capacity to prevent overload, but we also wanted to fix the server. Instead of exploding, it should…
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Book of the Runtime – Internals of the .Net Runtime not in the documentation
The Microsoft Docs at https://docs.microsoft.com are really fantastic lately. ...
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The Windows Shutdown crapfest (2006)
I worked at Microsoft for about 7 years total, from 1994 to 1998, and from 2002 to 2006. The most frustrating year of those seven was the ...
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Retina iMac owners can greatly improve graphics performance of many applications
Hmph! Not sure which one is "correct" there... hmm... If you use kCGImageAlphaPremultipliedFirst for the CGBitmapContext rather than kCGImageAlphaNoneFirst, then it looks closer to the original, maybe. ? Also other caveat: NSBitmapImageRep can't seem to deal with the ARGB format either, so if you use that you need to…
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What Have We Learned from the PDP-11?
This post is a slightly edited version of my November presentation to the San Francisco chapter of Papers We Love.
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Hotswapping Haskell
Bluesky: @simonmar.bsky.social Github: simonmar Email: marlowsd@gmail.com LinkedIn: Simon Marlow