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The Two Faces of AMP
Tim Kadlec writes about performance, product management, and the web.
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Validating UTF-8 bytes using only 0.45 cycles per byte (AVX edition)
When receiving bytes from the network, we often assume that they are unicode strings, encoded using something called UTF-8. Sadly, not all streams of bytes are valid UTF-8. So we need to check the strings. It is probably a good idea to optimize this problem as much as possible. In earlier work, we showed that ……
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Anatomy of a Ceph meltdown
Last week, the server farm of our LMU Student Council had a major downtime over almost five days. As part of the administrator team there, I’d like to publish this post mortem to share our experiences and lessons learned to avoid situations like this in the future.
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AWS EC2 T2 Instances Demystified: Don’t Learn the Hard Way
How T2 burstable instances and CPU credits really work, with a worked example of a busy t2.micro running out of credits and grinding to a halt.
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A look at VDO, the new Linux compression layer
Use Red Hat Enterprise Linux 7.5's VDO for storage optimization - save space, boost performance
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96-core ARM supercomputer using the NanoPi-Fire3
Building a high performance supercomputer for under £100 (£550 including twelve Fire3s). Parts list, benchmarks and downloadable plans for laser-cutting the acrylic case.
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You can't contain me: elevation-of-privilege vulnerability in Docker for Windows
I have been continuing my journey of searching for windows breakout vulnerabilities in popular applications and one that I discovered in March I found intere...
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Qubes OS 4.0 has been released
After nearly two years in development and countless hours of testing, we’re pleased to announce the stable release of Qubes OS 4.0! Major changes in version 4.0 Version 4.0 includes several fundamental improvements to the security and functionality of Qubes OS: The Qubes Admin API Qubes...
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Optimal Shard Placement in a Petabyte Scale Elasticsearch Cluster
At the heart of Meltwater’s and Fairhair.ai’s information retrieval systems lies a collection of Elasticsearch clusters containing billions of social media posts and editorial articles. The index shards in our clusters vary greatly in their access pattern, workload and size which presents some very interesting…
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GCC 8 Link Time and Interprocedural Optimization
GCC 8.1 was released and Linux distros are starting to pick it up. This week hit the openSUSE Thumbleweed update with full rebuild (thanks t...
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Two-phase commit and beyond
In this post, we model and explore the two-phase commit protocol using TLA+. The two-phase commit protocol is practical and is used in man...
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ServiceFabric: a distributed platform for building microservices in the cloud
ServiceFabric: a distributed platform for building microservices in the cloud Kakivaya et al., EuroSys’18 (If you don’t have ACM Digital Library access, the paper can be accessed either by fo…
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LLVM’s garbage collection facilities and SBCL’s generational GC
Intro, overview
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Faster – A key-value store for large state management
At SIGMOD 2018, a team from Microsoft Research will be presenting a new embedded key-value store called FASTER, described in their paper “FASTER: A Concurrent Key-Value Store with In-Place Updates”. As its name suggests, FASTER makes a major leap forward in terms of supporting fast and frequent lookups and updates of…
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Fedora 29
[This message comes directly from the desk of the Fedora Project Leader. — Ed.] In just one week, it will be fifteen years since we announced the release of Fedora Core 1. Now, we’re announcing the release of Fedora 29 — now not just “core”, but Workstation, Server, Atomic Host, a whole collection of desktop Spins […]
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Redshift – A better flux program for Linux (2014)
F.lux is a wonderful tool for helping eye strain. People who stare at computer screens all day (like myself) can experience quite a bit of eye strain due to the harsh lights screens emit. One solution is to wear yellow tinted gamer goggles. I chose the cheaper route, installing software to adjust the color temperature…
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The Road to QUIC
QUIC (Quick UDP Internet Connections) is a new encrypted-by-default Internet transport protocol, that provides a number of improvements designed to accelerate HTTP traffic as well as make it more secure, with the intended goal of eventually replacing TCP and TLS on the web.
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Global Kernel Locks in APFS
Over the past several months, a handful of people had been complaining that Mercurial's test harness was executing much slower on Macs. But this slowdown seemingly wasn't occurring on Linux or Windows. And not every Mac user experienced the slowness!
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Memory-Level Parallelism: Intel Skylake versus Apple A12/A12X
Modern processors execute instructions in parallel in many different ways: multi-core parallelism is just one of them. In particular, processor cores can have several outstanding memory access requests "in flight". This is often described as "memory-level parallelism". You can measure the level of memory-level…
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A timesyncd failure and systemd's lack of debugability
You're probably reading this page because you've attempted to access some part of my blog (Wandering Thoughts) or CSpace , the wiki thing it's part of. Unfortunately you're using a browser version that my anti-crawler precautions consider suspicious, most often because it's too old (most often this applies to versions…
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A look at home routers, and a surprising bug in Linux/MIPS
Xôi Lạc TV là địa chỉ theo dõi bóng đá trực tuyến được người dùng đánh giá cao. Với hàng loạt giải đấu được phát sóng miễn phí cùng nhiều thông tin được cập nhật như lịch thi đấu, kết quả, bảng xếp hạng, tỷ số và những tin tức thể thao đáng chú ý.
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PostgreSQL 10: Partitions of partitions
PostgreSQL version 10 brings a much anticipated feature: (Native) Table Partitioning .
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From VNC to reverse shell
Personal websites are weird. We are mostly past the era of having them, as things like twitter and hosted blog services like Medium have taken them over, but I’m a hold out. I run both my own blog, and have a landing page on the apex domain since the server that hosts the blog (Google App Engine + Cloudflare) is…
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Building a Distributed Log from Scratch: Sketching a New System
In part four of this series we looked at some key trade-offs involved with a distributed log implementation and discussed a few lessons learned while building NATS Streaming. In this fifth and final installment, we’ll conclude by outlining the design for a new log-based system that draws from the previous entries in…
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Improving compression at scale with Zstandard
Two years ago, Facebook open-sourced Zstandard v1.0, a landmark data compression solution that offers best-in-kind performance. Since then, we’ve released a variety of enhancements and advanc…
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Validating UTF-8 strings using as little as 0.7 cycles per byte
Most strings found on the Internet are encoded using a particular unicode format called UTF-8. However, not all strings of bytes are valid UTF-8. The rules as to what constitute a valid UTF-8 string are somewhat arcane. Yet it seems important to quickly validate these strings before you consume them. In a previous…