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9b02094827
The primary effect of this change is to simplify the implementation of the priority mempool to eliminate an unbounded heap growth observed by Vega team when it was enabled in their testnet. It updates and fixes #8775. The main body of this change is to remove the auxiliary indexing structures, and use only the concurrent list structure (the same as the legacy mempool) to maintain both gossip order and priority. This means that operations that require priority information, such as block updates and insert-time evictions, require a linear scan over the mempool. This tradeoff greatly simplifies the code and eliminates the long-term heap load, at the cost of some extra CPU and short-lived working memory during CheckTx and Update calls. Rough benchmark results: - This PR: BenchmarkTxMempool_CheckTx-10 486373 2271 ns/op - Original priority mempool implementation: BenchmarkTxMempool_CheckTx-10 500302 2113 ns/op - Legacy (v0) mempool: BenchmarkCheckTx-10 364591 3571 ns/op These benchmarks are not a good proxy for production load, but at least suggest that the overhead of the implementation changes are not cause for concern. In addition: - Rework synchronization so that access to shared data structures is safe. Previously shared locks were used to exclude block updates during calls that update mempool state. Now access is properly exclusive where necessary. - Fix a bug in the recheck flow, where priority updates from the application were not correctly reflected in the index structures. - Eliminate the need for separate recheck cursors during block update. This avoids the need to explicitly invalidate elements of the concurrent list, which averts the dependency cycle that led to objects being pinned. - Clean up, clarify, and fix inaccuracies in documentation comments throughout the package. Co-authored-by: William Banfield <4561443+williambanfield@users.noreply.github.com>