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Systems & Performance

The most popular blog posts about systems & performance on Hacker News. 271 posts.

2018
96

Fast base64 encoding and decoding

Computers store data as streams of bits. Binary files like image, audio or video files are allowed to contain just about any sequence of bits. However, we also often use text formats; for example, web pages and emails are required to be text. So how do we send images by email? How do we embed … Continue reading…

100

Some thoughts on Spectre and Meltdown

The story of these attacks starts in late 2004. I had submitted my doctoral thesis and had a few months before flying back to Oxford for my defense, so I turned to some light reading: Intel's latest "Optimization Manual", full of tips on how to write faster code. (Eking out every last nanosecond of performance has…

104

Modern Linux in an ancient PC

What is the oldest x86 processor that is still supported by a modern Linux kernel in present time? I asked the above quiz question during the Geekcamp tech conference in Nov 2017 during my emcee role. The theoretical answer as you can glean from the title of this post is the 486 which was first released in 1989. I…

110

Spectre/Meltdown Pits Transparency Against Liability

There is a lot of righteous anger directed toward Intel over CPU bugs that were revealed by Spectre/Meltdown. I agree that things could have been handled better, particularly with regards to transparency and the sharing of information among the relevant user communities that could have worked together to deploy…

112

Modeling Message Queues in TLA+

I recently did a corporate TLA+ workshop and some people asked what TLA+ specs look like in practice. If you looked at the most common public examples, you’d probably come away thinking that people only used it for critical consensus algorithms. This is a problem for two reasons: first, it makes it harder to learn…

114

Speeding Up Ruby with Shared Strings

It’s not often I am able to write a patch that not only reduces memory usage, but increases speed as well. Usually I find myself trading memory for speed, so it’s a real treat when I can improve both in one patch. Today I want to talk about the patch I submitted to Ruby in this ticket. It decreases “after boot” memory…

117

How I wound up finding a bug in GNU Tar

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…

120

AVX-512: when and how to use these new instructions

Note: This blog post from 2018 predates the Intel Ice Lake (Sunny Core) and AMD Zen 4 processors. These newer processors are not affected by the issues described in this blog post. Our processors typically do computations using small data stores called registers. On 64-bit processors, 64-bit registers are frequently…