c0e91efdb3
dc1c17c085doc: add release notes (Andrew Toth)0e10937184fuzz: add coins_view_stacked fuzz harness to test concurrent leveldb reads (Andrew Toth)ce610a6ff4fuzz: update harnesses to cover CoinsViewOverlay::StartFetching (Andrew Toth)760fb22dc3test: add unit tests for CoinsViewOverlay::StartFetching (Andrew Toth)d69a3b20dedoc: update CoinsViewOverlay docstring to describe parallel fetching (Andrew Toth)ab2a379237coins: fetch inputs in parallel (Andrew Toth)fdf283036acoins: add ready flag to InputToFetch (Andrew Toth)ede11b8314validation: collect block inputs in CoinsViewOverlay before ConnectBlock (Andrew Toth)f82043af50coins: introduce thread pool in CoinsViewOverlay (Andrew Toth)5bf1c32008validation: add -prevoutfetchthreads configuration option (Andrew Toth) Pull request description: This PR is a continuation of https://github.com/bitcoin/bitcoin/pull/31132. All outstanding issues raised there have been resolved, but the volume of stale comments can make that change difficult to review. Currently, when connecting a block, each input prevout is looked up one at a time. For every input we first check the in-memory coins cache, and on a miss we make a synchronous round-trip to the chainstate LevelDB to read the coin from disk. Because these lookups happen serially as the block is being validated, the disk read latency stacks up and dominates the time spent in `ConnectBlock` whenever many inputs are not already in the cache. This PR moves those disk reads onto a pool of worker threads that run in parallel with block connection. Before entering `ConnectBlock` the block is handed to a `CoinsViewOverlay`, which kicks off the workers to begin fetching all of the block's prevouts from disk and warming the cache. The main validation thread continues to do exactly the same work it does today, hitting the cache for each input in order. The only difference is that by the time it asks, the coin is much more likely to already be there. There are no validation logic or consensus behavior changes. This is purely a parallelization of an existing read pattern. The number of fetcher threads is configurable via `-prevoutfetchthreads=<n>`, defaulting to 8 and capped at 16. Setting it to 0 disables input fetching entirely and reverts to the previous serial behavior. We have measured large performance gains for IBD and `-reindex-chainstate`, as well as worst-case steady-state block connection at the tip. l0rinc ran many thorough benchmarking passes on the original PR across multiple machines, storage types, dbcache sizes[^1], operating systems[^2], and fetcher thread counts[^3]. Many other contributors also posted their benchmark results in the original PR. IBD speedups range from 1.18× to over 3× faster[^4]. Worst-case block connection time for network-attached storage was over 2× faster[^5]. Flamegraph comparisons before and after this change are available[^6]. On safety: `ConnectBlock` runs while holding `cs_main`, so nothing else in the node can mutate the chainstate while the fetchers are reading it. On LevelDB: [concurrent reads are fully supported](https://github.com/bitcoin/bitcoin/blob/master/src/leveldb/include/leveldb/db.h#L44) and [documented as such](https://github.com/bitcoin/bitcoin/blob/master/src/leveldb/doc/index.md#concurrency). We already rely on this in production today against our other LevelDB-backed databases. The `txindex` DB is read by multiple simultaneous HTTP RPC worker threads via the `getrawtransaction` RPC. The `blockfilterindex` DB is called concurrently from both the P2P `cfilters` / `cfheaders` / `cfcheckpt` message handlers on the `msghand` thread, and from the `getblockfilter` RPC on the HTTP RPC worker threads. We have not yet been issuing concurrent reads against the chainstate DB, but there is no LevelDB-side reason we can't. In fact, the chainstate DB is already being touched by more than one thread on master, because LevelDB schedules its own background compaction work. For reviewers: The main change is `CoinsViewOverlay` gets 1 new public and 2 new private methods. - `StartFetching`: public method called in lieu of `CreateResetGuard` before we enter `ConnectBlock`. It still returns a `ResetGuard` so the view is `Reset` before the block it is working on leaves scope. This kicks off worker threads who each just run `while (ProcessInput()) {}` and then return. - `StopFetching`: private method called on `Reset` whenever the guard leaves scope or `Flush`. Stops all threads and clears multi threaded state. - `ProcessInput`: private method that fetches a single input prevout. Returns `true` if an input was fetched and `false` otherwise. This is the only method on `CoinsViewOverlay` that is called concurrently by multiple threads. Every other method on the overlay is still called synchronously on the main thread. The `CoinsViewOverlay::FetchCoinFromBase` method is also extended to lookup the coins fetched from `ProcessInput` first before falling back to `base->PeekCoin`. Mutating methods `Reset` and `Flush` are overridden in `CoinsViewOverlay` to call `StopFetching` first. [^1]: https://github.com/bitcoin/bitcoin/pull/31132#pullrequestreview-3515011880 [^2]: https://github.com/bitcoin/bitcoin/pull/31132#issuecomment-3767758819 [^3]: https://github.com/bitcoin/bitcoin/pull/31132#issuecomment-3617721711 [^4]: https://github.com/bitcoin/bitcoin/pull/31132#issuecomment-3678847806 [^5]: https://github.com/bitcoin/bitcoin/pull/31132#issuecomment-4071032270 [^6]: https://github.com/bitcoin/bitcoin/pull/31132#issuecomment-3617315125 ACKs for top commit: l0rinc: reACKdc1c17c085willcl-ark: ACKdc1c17c085theStack: re-ACKdc1c17c085ryanofsky: Code review ACKdc1c17c085with changes to StopFetching and AllInputsConsumed checking behavior since last review. Tree-SHA512: 89c1c2890f65aac5cd546edc44504956c47b6fada256d3b86ced47e6dd8c72f633a4357753b3b9805b9ba6ed02790822090d70578aba2964baf50d7eb956864c
Bitcoin Core integration/staging tree
For an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/.
What is Bitcoin Core?
Bitcoin Core connects to the Bitcoin peer-to-peer network to download and fully validate blocks and transactions. It also includes a wallet and graphical user interface, which can be optionally built.
Further information about Bitcoin Core is available in the doc folder.
License
Bitcoin Core is released under the terms of the MIT license. See COPYING for more information or see https://opensource.org/license/MIT.
Development Process
The master branch is regularly built (see doc/build-*.md for instructions) and tested, but it is not guaranteed to be
completely stable. Tags are created
regularly from release branches to indicate new official, stable release versions of Bitcoin Core.
The https://github.com/bitcoin-core/gui repository is used exclusively for the development of the GUI. Its master branch is identical in all monotree repositories. Release branches and tags do not exist, so please do not fork that repository unless it is for development reasons.
The contribution workflow is described in CONTRIBUTING.md and useful hints for developers can be found in doc/developer-notes.md.
Testing
Testing and code review is the bottleneck for development; we get more pull requests than we can review and test on short notice. Please be patient and help out by testing other people's pull requests, and remember this is a security-critical project where any mistake might cost people lots of money.
Automated Testing
Developers are strongly encouraged to write unit tests for new code, and to
submit new unit tests for old code. Unit tests can be compiled and run
(assuming they weren't disabled during the generation of the build system) with: ctest. Further details on running
and extending unit tests can be found in /src/test/README.md.
There are also regression and integration tests, written
in Python.
These tests can be run (if the test dependencies are installed) with: build/test/functional/test_runner.py
(assuming build is your build directory).
The CI (Continuous Integration) systems make sure that every pull request is tested on Windows, Linux, and macOS. The CI must pass on all commits before merge to avoid unrelated CI failures on new pull requests.
Manual Quality Assurance (QA) Testing
Changes should be tested by somebody other than the developer who wrote the code. This is especially important for large or high-risk changes. It is useful to add a test plan to the pull request description if testing the changes is not straightforward.
Translations
Changes to translations as well as new translations can be submitted to Bitcoin Core's Transifex page.
Translations are periodically pulled from Transifex and merged into the git repository. See the translation process for details on how this works.
Important: We do not accept translation changes as GitHub pull requests because the next pull from Transifex would automatically overwrite them again.