Changing std::sort at Google’s Scale and Beyond
TL;DR; We are changing std::sort in LLVM’s libcxx. That’s a long story of what it took us to get there and all possible consequences, bugs you might encounter with examples from open source. We provide some benchmarks, perspective, why we did this in the first place and what it cost us with exciting ideas from…
Beyond malloc efficiency to fleet efficiency: a hugepage-aware memory allocator
TCMalloc team recently published a paper on OSDI’21 about Google’s allocator internals, specifically on how huge pages are used. You can read the full paper here. TL;DR. Google saved 2.4% of the memory fleet and increased the QPS performance of the most critical applications by 7.7%, an impressive result worth noting. Code is open sourced,…
How a Bug(?) in the Linux CRC-32 Checksum Turned out not to be a Bug
A friend of mine nerd sniped me with a good story to investigate which kinda made me giggle and want to tell to the public some cool things happened to me during my experience with hashing and other stuff. The story is simple and complex at the same time, I’d try to stick to a…
Miniselect: Practical and Generic Selection Algorithms
Today I present a big effort from my side to publish miniselect — generic C++ library to support multiple selection and partial sorting algorithms. It is already used in ClickHouse with huge performance benefits. Exact benchmarks and results will be later in this post and now let’s tell some stories about how it all arose.…
I need extra C/C++ performance now. How?
Hello everyone, today we are going to talk about C++ performance. Again, another “usual” perf blog as you may think. I promise to give really practical advice and don’t get bullshitty (okay, a little bit) talks about how C++ is performant. We are gonna roast the compilers and think about what we should do about…
News Aggregator from Scratch in 2 Weeks
Data Clustering Contest was a two-week data science and engineering competition held by Telegram in May. The Telegram team wanted participants to build a simple yet effective news aggregator that consolidates thousands of articles from various publishers and websites into a single page, which shows the latest news in real time, exactly like Google News, Bing News or…
Optimizing 128-bit Division
When it comes to hashing, sometimes 64 bit is not enough, for example, because of birthday paradox — the hacker can iterate through random 
Why is std::pair broken?
Today we are going to talk about C++ basic std::pair class in a way how and why it is broken. Story std::pair first appeared in C++98 as a pretty basic class with a very simple semantics — you have two types T1 and T2, you can write std::pair<T1, T2> and access .first and .second members…
How to crack HashCode competition with some engineering skills
Hi everyone, hashcode is over. As now I can tell anything, I want just to tell how I was solving this problem, my methodologies, overall the structure of the data sets. I am not going to provide any internals and whatsoever, all data can be checked and much of it is my personal opinion though…
I wrote Go code for 3 weeks and you won’t believe what happened next
Historically, I am a C++ programmer and really like all this kind of C-ish stuff — from raw assembly to high level abstractions and SFINAE methods. For the past three weeks I managed to write lots of Go code — around 10k LOC without almost knowing anything when I started. I want to talk what…
How to contribute to Abseil with a visible performance gain
Overview of Abseil Abseil is a great C++ library with a special and unique philosophy inside it. While there is a lot of debate what C++ is prioritizing more – portability or performance with possibly breaking changes, Abseil library aims in a standard compatible way to provide best library features of all standards sometimes with…
About me and this blog
I am Danila Kutenin. I am an engineer working at Google and doing distributed and high performance C++ software. My main interests are distributed systems, operating systems design, hardware testing, compilers, APIs, algorithms and theoretical computer science. I worked for almost for 2 years at Yandex doing the core search engine – one of the…
Experimental chill 