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Before this commit, we would always prepare tracepoint arguments regardless of the tracepoint being used or not. While we already made sure not to include expensive arguments in our tracepoints, this commit introduces gating to make sure the arguments are only prepared if the tracepoints are actually used. This is a win-win improvement to our tracing framework. For users not interested in tracing, the overhead is reduced to a cheap 'greater than 0' compare. As the semaphore-gating technique used here is available in bpftrace, bcc, and libbpf, users interested in tracing don't have to change their tracing scripts while profiting from potential future tracepoints passing slightly more expensive arguments. An example are mempool tracepoints that pass serialized transactions. We've avoided the serialization in the past as it was too expensive. Under the hood, the semaphore-gating works by placing a 2-byte semaphore in the '.probes' ELF section. The address of the semaphore is contained in the ELF note providing the tracepoint information (`readelf -n ./src/bitcoind | grep NT_STAPSDT`). Tracing toolkits like bpftrace, bcc, and libbpf increase the semaphore at the address upon attaching to the tracepoint. We only prepare the arguments and reach the tracepoint if the semaphore is greater than zero. The semaphore is decreased when detaching from the tracepoint. This also extends the "Adding a new tracepoint" documentation to include information about the semaphores and updated step-by-step instructions on how to add a new tracepoint.
Bitcoin Core
Setup
Bitcoin Core is the original Bitcoin client and it builds the backbone of the network. It downloads and, by default, stores the entire history of Bitcoin transactions, which requires several hundred gigabytes or more of disk space. Depending on the speed of your computer and network connection, the synchronization process can take anywhere from a few hours to several days or more.
To download Bitcoin Core, visit bitcoincore.org.
Running
The following are some helpful notes on how to run Bitcoin Core on your native platform.
Unix
Unpack the files into a directory and run:
bin/bitcoin-qt(GUI) orbin/bitcoind(headless)
Windows
Unpack the files into a directory, and then run bitcoin-qt.exe.
macOS
Drag Bitcoin Core to your applications folder, and then run Bitcoin Core.
Need Help?
- See the documentation at the Bitcoin Wiki for help and more information.
- Ask for help on Bitcoin StackExchange.
- Ask for help on #bitcoin on Libera Chat. If you don't have an IRC client, you can use web.libera.chat.
- Ask for help on the BitcoinTalk forums, in the Technical Support board.
Building
The following are developer notes on how to build Bitcoin Core on your native platform. They are not complete guides, but include notes on the necessary libraries, compile flags, etc.
- Dependencies
- macOS Build Notes
- Unix Build Notes
- Windows Build Notes
- FreeBSD Build Notes
- OpenBSD Build Notes
- NetBSD Build Notes
Development
The Bitcoin repo's root README contains relevant information on the development process and automated testing.
- Developer Notes
- Productivity Notes
- Release Process
- Source Code Documentation (External Link)
- Translation Process
- Translation Strings Policy
- JSON-RPC Interface
- Unauthenticated REST Interface
- BIPS
- Dnsseed Policy
- Benchmarking
- Internal Design Docs
Resources
- Discuss on the BitcoinTalk forums, in the Development & Technical Discussion board.
- Discuss project-specific development on #bitcoin-core-dev on Libera Chat. If you don't have an IRC client, you can use web.libera.chat.
Miscellaneous
- Assets Attribution
- bitcoin.conf Configuration File
- CJDNS Support
- Files
- Fuzz-testing
- I2P Support
- Init Scripts (systemd/upstart/openrc)
- Managing Wallets
- Multisig Tutorial
- Offline Signing Tutorial
- P2P bad ports definition and list
- PSBT support
- Reduce Memory
- Reduce Traffic
- Tor Support
- Transaction Relay Policy
- ZMQ
License
Distributed under the MIT software license.