Andrei Eres
ec7bfae00a
## Why we need it To provide another level of understanding to why polkadot's subsystems may perform slower than expected. Cache misses occur when processing large amounts of data, such as during availability recovery. ## Why Cachegrind Cachegrind has many drawbacks: it is slow, it uses its own cache simulation, which is very basic. But unlike `perf`, which is a great tool, Cachegrind can run in a virtual machine. This means we can easily run it in remote installations and even use it in CI/CD to catch possible regressions. Why Cachegrind and not Callgrind, another part of Valgrind? It is simply empirically proven that profiling runs faster with Cachegrind. ## First results First results have been obtained while testing of the approach. Here is an example. ``` $ target/testnet/subsystem-bench --n-cores 10 --cache-misses data-availability-read $ cat cachegrind_report.txt I refs: 64,622,081,485 I1 misses: 3,018,168 LLi misses: 437,654 I1 miss rate: 0.00% LLi miss rate: 0.00% D refs: 12,161,833,115 (9,868,356,364 rd + 2,293,476,751 wr) D1 misses: 167,940,701 ( 71,060,073 rd + 96,880,628 wr) LLd misses: 33,550,018 ( 16,685,853 rd + 16,864,165 wr) D1 miss rate: 1.4% ( 0.7% + 4.2% ) LLd miss rate: 0.3% ( 0.2% + 0.7% ) LL refs: 170,958,869 ( 74,078,241 rd + 96,880,628 wr) LL misses: 33,987,672 ( 17,123,507 rd + 16,864,165 wr) LL miss rate: 0.0% ( 0.0% + 0.7% ) ``` The CLI output shows that 1.4% of the L1 data cache missed, which is not so bad, given that the last-level cache had that data most of the time missing only 0.3%. Instruction data of the L1 has 0.00% misses of the time. Looking at an output file with `cg_annotate` shows that most of the misses occur during reed-solomon, which is expected.
NOTE: We have recently made significant changes to our repository structure. In order to streamline our development process and foster better contributions, we have merged three separate repositories Cumulus, Substrate and Polkadot into this repository. Read more about the changes here.
Polkadot SDK
The Polkadot SDK repository provides all the resources needed to start building on the Polkadot network, a multi-chain blockchain platform that enables different blockchains to interoperate and share information in a secure and scalable way. The Polkadot SDK comprises three main pieces of software:
Polkadot
Implementation of a node for the https://polkadot.network in Rust, using the Substrate framework. This directory
currently contains runtimes for the Polkadot, Kusama, Westend, and Rococo networks. In the future, these will be
relocated to the runtimes repository.
Substrate
Substrate is the primary blockchain SDK used by developers to create the parachains that make up the Polkadot network. Additionally, it allows for the development of self-sovereign blockchains that operate completely independently of Polkadot.
Cumulus
Cumulus is a set of tools for writing Substrate-based Polkadot parachains.
Upstream Dependencies
Below are the primary upstream dependencies utilized in this project:
Security
The security policy and procedures can be found in docs/contributor/SECURITY.md.
Contributing & Code of Conduct
Ensure you follow our contribution guidelines. In every interaction and contribution, this project adheres to the Contributor Covenant Code of Conduct.
Additional Resources
- For monitoring upcoming changes and current proposals related to the technical implementation of the Polkadot network,
visit the
Requests for Comment (RFC)repository. While it's maintained by the Polkadot Fellowship, the RFC process welcomes contributions from everyone.