How a Single Line of Code Made a 24-Core Server Slower Than a Laptop

• nosqlbench

  4 159 9.9 Java

  The open source, pluggable, nosql benchmarking suite.

  

Not directly related, but https://github.com/nosqlbench/nosqlbench is very flexible benchmark tool for Cassandra and other distributed systems

• Folly

  90 27,072 9.8 C++

  An open-source C++ library developed and used at Facebook.

  

Can't speak for abseil and tbb, but in folly there are a few solutions for the common problem of sharing state between a writer that updates it very infrequently and concurrent readers that read it very frequently (typical use case is configs).

The most performant solutions are RCU (https://github.com/facebook/folly/blob/main/folly/synchroniz...) and hazard pointers (https://github.com/facebook/folly/blob/main/folly/synchroniz...), but they're not quite as easy to use as a shared_ptr [1].

Then there is simil-shared_ptr implemented with thread-local counters (https://github.com/facebook/folly/blob/main/folly/experiment...).

If you absolutely need a std::shared_ptr (which can be the case if you're working with pre-existing interfaces) there is CoreCachedSharedPtr (https://github.com/facebook/folly/blob/main/folly/concurrenc...), which uses an aliasing trick to transparently maintain per-core reference counts, and scales linearly, but it works only when acquiring the shared_ptr, any subsequent copies of that would still cause contention if passed around in threads.

[1] Google has a proposal to make a smart pointer based on RCU/hazptr, but I'm not a fan of it because generally RCU/hazptr guards need to be released in the same thread that acquired them, and hiding them in a freely movable object looks like a recipe for disaster to me, especially if paired with coroutines https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p05...

• InfluxDB

  www.influxdata.com sponsored

  Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.

  

• FlameGraph

  53 16,406 4.9 Perl

  Stack trace visualizer

Small note:

> In Rust, it is very easy to generate flamegraphs with `cargo flamegraph`.

... Also in pretty much every other language, because this is just a wrapper around Brendan Gregg's FlameGraph visualizer: https://github.com/brendangregg/FlameGraph

• linux

  980 170,074 10.0 C

  Linux kernel source tree

https://github.com/torvalds/linux/commit/8e86f0b409a44193f15... was the commit that fixed this IIRC

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