Hacker GitHub

← All repos

meta/folly

View on GitHub ↗ ★ 30,556 C++

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

144 mentions on Hacker News by 90 people: 15 stories, 129 comments · first 2012-06-02 · latest 2026-01-14

Mentions per year 144 mentions · busiest year 2020 (16)
20082026
AllStoriesComments NewestTopOldest
  1. …trials and look at the minimum observed time, which is when there will have been ~no interruptions. https://github.com/facebook/folly/blob/main/folly/docs/Bench...
    comment by loeg · 2026-01-14 · in A 40-line fix eliminated a 400x performance gap
  2. …Not saying those are precisely on point, though; just thought some of the ideas were similar. [0]: https://github.com/facebook/folly/blob/main/folly/docs/Poly.... [1]: https://github.com/microsoft/proxy
    comment by aw1621107 · 2025-12-19 · in Common Rust Lifetime Misconceptions
  3. …Folly's definition [1]. [0] https://community.intel.com/t5/Intel-Moderncode-for-Parallel... [1] https://github.com/facebook/folly/blob/d2e6fe65dfd6b30a9d504...
    comment by charleshn · 2025-12-08 · in Spinlocks vs. Mutexes: When to Spin and When to Sleep
  4. …in C++ in a very similar way as Rust. E.g., APIs can take folly::Synchronized<T>::RLockedPtr: https://github.com/facebook/folly/blob/76f81836a2ccb6cd3bc7d...
    comment by loeg · 2025-09-23 · in The allure of new languages vs. the necessity of problem-solving
  5. …mostly historical, though it's relatively common to use a 128 byte line size on x86, still. E.g., https://github.com/facebook/folly/blob/main/folly/lang/Align... (Sandy Bridge was a 2011 CPU). (Clang's impl of the std version of these…
    comment by loeg · 2025-09-15 · in Analyzing the memory ordering models of the Apple M1
  6. …every single time they need to do some basic things (like for example version upgrades). Example: https://github.com/facebook/folly/blob/main/build.sh
    comment by dev_l1x_be · 2025-09-15 · in RustGPT: A pure-Rust transformer LLM built from scratch
  7. https://github.com/facebook/folly/blob/main/folly/chrono/Har...
    comment by loeg · 2025-08-16 · in OpenBSD is so fast, I had to modify the program slightly to measure itself
  8. …on escape-heavy strings. [1] https://source.chromium.org/chromium/_/chromium/v8/v8/+/5cbc... [2] https://github.com/facebook/folly/commit/2f0cabfb48b8a8df84f...
    comment by ot · 2025-08-04 · in How we made JSON.stringify more than twice as fast
  9. Bingo. https://github.com/facebook/folly/commit/4d932ecc53c7a722671...
    comment by loeg · 2025-05-07 · in Matt Godbolt sold me on Rust by showing me C++
  10. …[3]: https://research.facebook.com/publications/hive-a-warehousin... [4]: https://github.com/facebook/folly/tree/main
    comment by smitelli · 2024-12-04 · in Meta built large-scale cryptographic monitoring
  11. …some are better at certain workloads than the rest. DistributedMutex and SharedMutex come to mind ( https://github.com/facebook/folly/blob/main/folly/synchroniz... , https://github.com/facebook/folly/blob/main/folly/SharedMute... ) Just…
    comment by uvdn7 · 2024-10-02 · in The Fastest Mutexes
  12. …look at it? Wondering if there are any advantages. The api seems fairly similar to me at a glance. https://github.com/facebook/folly/tree/main/folly/experiment...
    comment by dkasper · 2024-09-26 · in Show HN: Coros – A Modern C++ Library for Task Parallelism
  13. …disprove your wrong assertions as opposed to providing references that justify your position: Folly https://github.com/facebook/folly : "It complements (as opposed to competing against) offerings such as Boost and of course std. In fact,…
    comment by Maxatar · 2024-08-06 · in C++'s `noexcept` can sometimes help or hurt performance
  14. …used to test its core synchronization primitives, but I don't think it's as sophisticated as loom. https://github.com/facebook/folly/blob/main/folly/test/Deter...
    comment by ot · 2024-07-06 · in Properly testing concurrent data structures
  15. Easily solved manually reserving exponentially. All my projects use some variation of this: https://github.com/facebook/folly/blob/9f125c94e10fd01f5567c... But I've burned myself on this a few times before.
    comment by mandarax8 · 2024-06-09 · in Compilers are too smart
  16. Modern hash table implementations use vector instructions for lookups: - Folly: https://github.com/facebook/folly/blob/main/folly/container/... - Abseil: https://abseil.io/about/design/swisstables
    comment by alexhutcheson · 2024-06-04 · in Intel's Lion Cove Architecture Preview
  17. Nope, given that it has a plugin architecture and in time it would have been everywhere. https://github.com/facebook/folly/commit/b1391e1c57be71c1e2a...
    comment by pajko · 2024-03-31 · in Ask HN: How bad is the xz hack?
  18. yes, like this one: https://github.com/facebook/folly/pull/2153
    comment by jdright · 2024-03-30 · in Backdoor in upstream xz/liblzma leading to SSH server compromise
  19. …correct.) And if they don't need the 2nd load on Linux, I'm unclear on why they do it. [0]: https://github.com/facebook/folly/blob/main/folly/synchroniz... (This uses either mprotect to force a TLB flush in process-relevant CPUs, or the…
    comment by loeg · 2024-03-01 · in A lock-free ring-buffer with contiguous reservations (2019)
  20. …but uses some sort of SeqCst barrier between the store and the 2nd load (with acquire semantics): https://github.com/facebook/folly/blob/main/folly/synchroniz...
    comment by loeg · 2024-03-01 · in A lock-free ring-buffer with contiguous reservations (2019)
  21. folly provides functions to resize std::string & std::vector without initialization [0]. [0] https://github.com/facebook/folly/blob/3c8829785e3ce86cb821c...
    comment by terrelln · 2023-10-27 · in Appending to an std:string character-by-character: how does the capacity grow?
  22. It is doable, `folly::Expected` supports that: https://github.com/facebook/folly/blob/main/folly/test/Expec...
    comment by ot · 2023-09-30 · in How to Use Monadic Operations for `std:optional` in C++23
  23. …With BMI2 you can also use the PDEP instruction to accelerate the final select on a 64-bit block: https://github.com/facebook/folly/blob/main/folly/experiment...
    comment by ot · 2023-07-02 · in A compressed indexable bitset
  24. …was a non-negotiable. [1] https://github.com/ot/ds2i/ [2] https://github.com/pisa-engine/pisa [3] https://github.com/facebook/folly/blob/main/folly/experiment...
    comment by ot · 2023-07-01 · in A compressed indexable bitset
  25. C++ with folly's SCOPE_EXIT {} construct: https://github.com/facebook/folly/blob/main/folly/ScopeGuard...
    comment by loeg · 2023-06-21 · in Defer for Shell (2020)
  26. …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/sy…
    comment by ot · 2023-06-18 · in A single line of code made a 24-core server slower than a laptop (2021)
  27. …folly C++ library was something I'd point to for my junior engineers to get a sense of "good" C++ https://github.com/facebook/folly
    comment by personjerry · 2023-06-17 · in Ask HN: What are some of the most elegant codebases in your favorite language?
  28. …in the standard library this even spells out that the result has "at least the specified capacity" https://github.com/facebook/folly/blob/main/folly/container/... F14 is a linear map but I couldn't immediately find actual API…
    comment by tialaramex · 2023-04-12 · in Deduplicate a slice in Go, use sort or a map?
  29. …com/SerenityOS/serenity/blob/master/Kernel/Lo... I don't know why the article doesn't touch on these. https://github.com/facebook/folly/blob/main/folly/docs/Synch... https://github.com/facebook/folly/blob/main/folly/Synchroniz...
    comment by loeg · 2023-04-06 · in MutexProtected: A C++ Pattern for Easier Concurrency
  30. …? https://en.cppreference.com/w/cpp/atomic/atomic * folly::Synchronized, mentioned by ot57? https://github.com/facebook/folly/blob/main/folly/docs/Synch... * Boost synchronized data structures, -mentioned by mchicken 53?…
    comment by einpoklum · 2023-04-06 · in MutexProtected: A C++ Pattern for Easier Concurrency
  31. …object. It is generally the preferred synchronization utility at Meta and thus it is widely used. https://github.com/facebook/folly/blob/main/folly/docs/Synch...
    comment by ot · 2023-04-06 · in MutexProtected: A C++ Pattern for Easier Concurrency
  32. https://github.com/facebook/folly/blob/main/folly/docs/Synch...
    comment by ajtulloch · 2023-04-06 · in MutexProtected: A C++ Pattern for Easier Concurrency
  33. …people use Result in Rust. (And C++ std::optional<T> is somewhat similar to Rust's Option<T> type.) https://github.com/facebook/folly/blob/main/folly/Expected.h...
    comment by loeg · 2023-03-14 · in Switching from C++ to Rust
  34. You have to use something similar to https://github.com/facebook/folly/tree/main/folly/experiment... to solve this problem. It's a nasty bug that everyone encounters when first working with coroutines. (Similarly everyone will encounter…
    comment by somerando7 · 2022-10-04 · in C++20 coroutines: “The bug is in the C++ standard, not GCC.” (2020)
  35. https://github.com/facebook/folly/blob/main/folly/docs/Packe... is pretty awesome and I’ve personally gotten big wins from it. The parent mentioned Bloom Filters, HyperLogLog-type stuff is on that family tree and also very interesting and…
    comment by benreesman · 2022-07-22 · in Ask HN: What are some cool but obscure data structures you know about?
  36. …for this (see folly::dynamic[1]). We make extensive use of this at my (non-Facebook) job. [1] https://github.com/facebook/folly/blob/master/folly/docs/Dyn...
    comment by ollien · 2022-05-26 · in Parsing JSON faster with Intel AVX-512
  37. https://github.com/facebook/folly/blob/main/folly/docs/Overv... This has library contents: it’s a mix of various utilities - type conversion, data structures, memory management, random numbers, concurrency, etc.
    comment by ximeng · 2022-01-07 · in Folly: An open-source C++ library developed and used at Facebook
  38. The docs have a bit more detail about what is included: https://github.com/facebook/folly/blob/main/folly/docs/Overv...
    comment by MarkSweep · 2022-01-07 · in Folly: An open-source C++ library developed and used at Facebook
  39. Ideally they should be turned into open source projects. Google's https://abseil.io and Facebook's https://github.com/facebook/folly come to mind.
    comment by floatboth · 2021-12-25 · in Fix the unit test and open a giant hole everywhere
  40. …callable and can be moved but not copied). That's often preferable for storing functors. Example: https://github.com/facebook/folly/blob/main/folly/docs/Funct...
    comment by MauranKilom · 2021-12-13 · in The Evolutions of Lambdas in C++14, C++17 and C++20
  41. …For example, Facebook's Folly has been updated to use coroutines and is being widely adopted at FB: https://github.com/facebook/folly/tree/main/folly/experiment...
    comment by pavlov · 2021-11-01 · in C++ Coroutines Do Not Spark Joy
  42. …an even better performance implementation using sqrt. Might make sense to port that over to Rust. https://github.com/facebook/folly/blob/master/folly/stats/TD...
    comment by rogers18445 · 2021-09-15 · in How percentile approximation works and why it's more useful than averages
  43. Edit: Links to repos: https://github.com/pytorch/pytorch https://github.com/tensorflow/tensorflow https://github.com/facebook/folly
    comment by pdevr · 2021-08-24 · in Ask HN: What are the best publicly available FAMANG code repos?
  44. For example folly's vector performs this optimization: https://github.com/facebook/folly/blob/master/folly/docs/FBV...
    comment by kevincox · 2021-06-15 · in Linux with “memory folios”: a 7% performance boost when compiling the kernel
  45. …) good ( https://software.intel.com/content/www/us/en/develop/documen... ) options ( https://github.com/facebook/folly/tree/master/folly/concurre... ) out there." There are plenty of practical solutions to the safe memory reclamation…
    comment by pkhuong · 2021-06-01 · in Libdill: Structured Concurrency for C (2016)
  46. …ticks? http://www.cs.columbia.edu/~nahum/w6998/papers/sosp87-timing... Production implementation: https://github.com/facebook/folly/blob/master/folly/io/async...
    comment by EquallyJust · 2021-05-25 · in Need Something Sorted? Sleep on It
  47. folly::Function was added for exactly this reason I think https://github.com/facebook/folly/blob/master/folly/docs/Fun...
    comment by aptxkid · 2021-04-16 · in Why C++ Is Terrifying
  48. …1.5, any growth factor below 2 has this property, how far below 2 regulates how quickly it happens, https://github.com/facebook/folly/blob/master/folly/docs/FBV... > it can be mathematically proven that a growth factor of 2 is rigorously…
    comment by masklinn · 2021-04-14 · in Is WebAssembly magic performance pixie dust?
  49. …Facebook's Folly library also provides type erasure functionality: https://github.com/facebook/folly/blob/master/folly/docs/Pol... Google's Abseil is full of type erasure: https://abseil.io/ Here is Adobe's C++ library for ty
    comment by Kranar · 2021-03-13 · in An Object-Oriented Language for the '20s
  50. …of the standard library you find is better than third party options. [1] https://abseil.io/ [2] https://github.com/facebook/folly [3] https://github.com/electronicarts/EASTL [4] https://www.boost.org/
    comment by Kranar · 2021-03-09 · in “ISO obstructs adoption of standards by paywalling them”