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Self-hosting open-source buck2 #11

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aherrmann opened this issue Sep 21, 2022 · 4 comments
Closed

Self-hosting open-source buck2 #11

aherrmann opened this issue Sep 21, 2022 · 4 comments

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@aherrmann
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AFAIK the open source version of buck2 can currently only be built with cargo.
Making it self-hosting, i.e. to be able to build the open source buck2 with itself, could be a good milestone on the way to making it useful in open source use-cases.
This came up in discussion with @arlyon on how to build the open source version of buck2.

@arlyon
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arlyon commented Oct 3, 2022

There has been some movement on this issue, and I believe we are close pending a rust toolchain to actually run the actions.

@ndmitchell
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We can actually build buck2 with buck2, and do in the open source CI.

@sluongng
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@ndmitchell Perhaps you would want to adjust the doc in https://github.com/facebook/buck2/blob/f014edfff62a78dc2868c580edb8950f456a65ec/docs/bootstrapping.md a bit.

Especially:

Note that the resulting binary will be compiled without optimisations or jemalloc, so we recommend using the Cargo-produced binary in further development.

Does it mean the buck2 build :buck2 binary now comes with Jemalloc and other optimizations as default?

@ndmitchell
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It's still true that we don't have Jemalloc. I think its probably also true that we don't have optimisations. I created #403 for that. I don't think its a big deal to do that (different toolchain with optimisations, onboard jemalloc) but it's a bit of work.

facebook-github-bot pushed a commit that referenced this issue Jan 9, 2024
Summary: Pull Request resolved: facebookexperimental/allocative#11

Reviewed By: ndmitchell

Differential Revision: D52630519

Pulled By: stepancheg

fbshipit-source-id: 0ce683c4cdcdf00dde904a2368aa2032e571b513
facebook-github-bot pushed a commit that referenced this issue Feb 15, 2024
Summary:
The stack around D42099161 introduced the ability to dynamically set the log level via a debug-command. This requires using `tracing_subscriber::reload::Layer`. The implementation of that machinery is backed by a `RwLock` [here](https://fburl.com/code/4xv0ihpn). This `RwLock` is read locked once on every single `#[instrumentation]` call to check whether the instrumentation is active or not.

On top of that, something in our fbsource third-party config enables the `parking_lot` feature of `tracing_subscriber`. This means that this is a `parking_lot::RwLock`, not a `std::sync::RwLock`, which is bad because it's well known that parking lot has problems with excessive spinning.

What all that adds up to is that when you put `#[instrument]` on a super hot function in dice, you get dozens of threads that are all simultaneously doing this:

```
  thread #23, name = 'buck2-rt', stop reason = signal SIGSTOP
    frame #0: 0x000000000c94a1fa buck2`<parking_lot::raw_rwlock::RawRwLock>::lock_shared_slow + 122
    frame #1: 0x0000000007a80b54 buck2`<tracing_subscriber::layer::layered::Layered<tracing_subscriber::reload::Layer<tracing_subscriber::filter::layer_filters::Filtered<tracing_subscriber::fmt::fmt_layer::Layer<tracing_subscriber::registry::sharded::Registry, tracing_subscriber::fmt::format::DefaultFields, tracing_subscriber::fmt::format::Format, std::io::stdio::stderr>, tracing_subscriber::filter::env::EnvFilter, tracing_subscriber::registry::sharded::Registry>, tracing_subscriber::registry::sharded::Registry>, tracing_subscriber::registry::sharded::Registry> as tracing_core::subscriber::Subscriber>::enabled + 292
    frame #2: 0x000000000a172d77 buck2`<dice::legacy::incremental::dep_trackers::internals::Dep<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>> as dice::legacy::incremental::graph::dependencies::Dependency>::recompute::{closure#0} + 183
    frame #3: 0x000000000a03606c buck2`<futures_util::stream::futures_unordered::FuturesUnordered<core::pin::Pin<alloc::boxed::Box<dyn core::future::future::Future<Output = core::result::Result<(alloc::boxed::Box<dyn dice::legacy::incremental::graph::dependencies::ComputedDependency>, alloc::sync::Arc<dyn dice::legacy::incremental::graph::GraphNodeDyn>), dice::api::error::DiceError>> + core::marker::Send>>> as futures_util::stream::stream::StreamExt>::poll_next_unpin + 444
    frame #4: 0x0000000009fc4755 buck2`<dice::legacy::incremental::IncrementalEngine<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>>>::compute_whether_dependencies_changed::{closure#0} (.llvm.4229350879637282184) + 1733
    frame #5: 0x0000000009ef30d4 buck2`<dice::legacy::incremental::IncrementalEngine<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>>>::compute_whether_versioned_dependencies_changed::{closure#0}::{closure#0} + 228
    frame #6: 0x0000000009f194ec buck2`<buck2_futures::cancellable_future::CancellableFuture<<dice::legacy::incremental::IncrementalEngine<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>>>::new_dice_task::{closure#0}> as core::future::future::Future>::poll (.llvm.11181184606289051452) + 3500
    frame #7: 0x0000000009f04bbf buck2`<futures_util::future::future::map::Map<buck2_futures::cancellable_future::CancellableFuture<<dice::legacy::incremental::IncrementalEngine<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>>>::new_dice_task::{closure#0}>, buck2_futures::spawn::spawn_inner<<dice::legacy::incremental::IncrementalEngine<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>>>::new_dice_task::{closure#0}, dice::api::user_data::UserComputationData, futures_util::future::ready::Ready<()>>::{closure#0}> as core::future::future::Future>::poll + 31
    frame #8: 0x0000000009ff0339 buck2`<futures_util::future::future::flatten::Flatten<futures_util::future::future::Map<futures_util::future::ready::Ready<()>, buck2_futures::spawn::spawn_inner<<dice::legacy::incremental::IncrementalEngine<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>>>::new_dice_task::{closure#0}, dice::api::user_data::UserComputationData, futures_util::future::ready::Ready<()>>::{closure#1}>, <futures_util::future::future::Map<futures_util::future::ready::Ready<()>, buck2_futures::spawn::spawn_inner<<dice::legacy::incremental::IncrementalEngine<dice::legacy::key::StoragePropertiesForKey<buck2_build_api::actions::calculation::BuildKey>>>::new_dice_task::{closure#0}, dice::api::user_data::UserComputationData, futures_util::future::ready::Ready<()>>::{closure#1}> as core::future::future::Future>::Output> as core::future::future::Future>::poll + 201
    frame #9: 0x00000000093f9f22 buck2`<tokio::task::task_local::TaskLocalFuture<buck2_events::dispatch::EventDispatcher, core::pin::Pin<alloc::boxed::Box<dyn core::future::future::Future<Output = alloc::boxed::Box<dyn core::any::Any + core::marker::Send>> + core::marker::Send>>> as core::future::future::Future>::poll + 130
    frame #10: 0x000000000939fdcb buck2`<tracing::instrument::Instrumented<<buck2_build_api::spawner::BuckSpawner as buck2_futures::spawner::Spawner<dice::api::user_data::UserComputationData>>::spawn::{closure#0}> as core::future::future::Future>::poll + 139
    frame #11: 0x00000000091ca5a9 buck2`<tokio::runtime::task::core::Core<tracing::instrument::Instrumented<<buck2_build_api::spawner::BuckSpawner as buck2_futures::spawner::Spawner<dice::api::user_data::UserComputationData>>::spawn::{closure#0}>, alloc::sync::Arc<tokio::runtime::scheduler::multi_thread::handle::Handle>>>::poll + 169
    frame #12: 0x00000000091c1b22 buck2`<tokio::runtime::task::harness::Harness<tracing::instrument::Instrumented<<buck2_build_api::spawner::BuckSpawner as buck2_futures::spawner::Spawner<dice::api::user_data::UserComputationData>>::spawn::{closure#0}>, alloc::sync::Arc<tokio::runtime::scheduler::multi_thread::handle::Handle>>>::poll + 146
    frame #13: 0x000000000c920f6f buck2`<tokio::runtime::scheduler::multi_thread::worker::Context>::run_task + 895
    frame #14: 0x000000000c91f847 buck2`<tokio::runtime::scheduler::multi_thread::worker::Context>::run + 2103
    frame #15: 0x000000000c932264 buck2`<tokio::runtime::context::scoped::Scoped<tokio::runtime::scheduler::Context>>::set::<tokio::runtime::scheduler::multi_thread::worker::run::{closure#0}::{closure#0}, ()> + 52
    frame #16: 0x000000000c932169 buck2`tokio::runtime::context::runtime::enter_runtime::<tokio::runtime::scheduler::multi_thread::worker::run::{closure#0}, ()> + 441
    frame #17: 0x000000000c91efa6 buck2`tokio::runtime::scheduler::multi_thread::worker::run + 70
    frame #18: 0x000000000c906a50 buck2`<tracing::instrument::Instrumented<tokio::runtime::blocking::task::BlockingTask<<tokio::runtime::scheduler::multi_thread::worker::Launch>::launch::{closure#0}>> as core::future::future::Future>::poll + 160
    frame #19: 0x000000000c8f8af9 buck2`<tokio::loom::std::unsafe_cell::UnsafeCell<tokio::runtime::task::core::Stage<tracing::instrument::Instrumented<tokio::runtime::blocking::task::BlockingTask<<tokio::runtime::scheduler::multi_thread::worker::Launch>::launch::{closure#0}>>>>>::with_mut::<core::task::poll::Poll<()>, <tokio::runtime::task::core::Core<tracing::instrument::Instrumented<tokio::runtime::blocking::task::BlockingTask<<tokio::runtime::scheduler::multi_thread::worker::Launch>::launch::{closure#0}>>, tokio::runtime::blocking::schedule::BlockingSchedule>>::poll::{closure#0}> + 153
    frame #20: 0x000000000c90166b buck2`<tokio::runtime::task::core::Core<tracing::instrument::Instrumented<tokio::runtime::blocking::task::BlockingTask<<tokio::runtime::scheduler::multi_thread::worker::Launch>::launch::{closure#0}>>, tokio::runtime::blocking::schedule::BlockingSchedule>>::poll + 43
    frame #21: 0x000000000c90d9b8 buck2`<tokio::runtime::task::harness::Harness<tracing::instrument::Instrumented<tokio::runtime::blocking::task::BlockingTask<<tokio::runtime::scheduler::multi_thread::worker::Launch>::launch::{closure#0}>>, tokio::runtime::blocking::schedule::BlockingSchedule>>::poll + 152
    frame #22: 0x000000000c90b848 buck2`<tokio::runtime::blocking::pool::Inner>::run + 216
    frame #23: 0x000000000c9002ab buck2`std::sys_common::backtrace::__rust_begin_short_backtrace::<<tokio::runtime::blocking::pool::Spawner>::spawn_thread::{closure#0}, ()> + 187
    frame #24: 0x000000000c90042e buck2`<<std::thread::Builder>::spawn_unchecked_<<tokio::runtime::blocking::pool::Spawner>::spawn_thread::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} + 158
    frame #25: 0x000000000757e4b5 buck2`std::sys::unix::thread::Thread::new::thread_start::h618b0b8e7bda0b2b + 37
    frame #26: 0x00007f2ba1e9abaf
```

This hit an open source user super hard over in #555 .

This diff approaches this issue by putting all the `#[instrument]`s in dice behind `#[cfg(debug_assertions)]`. This allows them to still be used in debug mode, but keeps them out of any hot paths. I do not have numbers to show that most of these matter. The only one I know matters for sure is `recompute`.

Alternatives are to either try and tailor this to the callsites we know are hot (that sounds error prone) or to revert the stack that inadvertently introduced the RwLock. Even if we did that though, it's probably still safer to keep `#[instrument]` out of super hot paths like this.

Reviewed By: stepancheg

Differential Revision: D53744041

fbshipit-source-id: 85bce9af2fec8ad1d50adc241d3b8e2bfc5cec87
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