coin pointer + pr35295#175
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Introduce CoinsViewOverlay::StartFetching, which maps all input prevouts of a block to a new m_inputs vector of InputToFetch elements. Returns a ResetGuard which is lifetime bound to the block, while the InputToFetch elements are lifetime bound to the block as well. Introduce StopFetching to clear the m_inputs vector. CCoinsViewCache::Reset is made virtual and is overridden in CoinsViewOverlay. StopFetching is called on Reset, so the InputToFetch objects will not exceed the lifetime of the block. Introduce ProcessInput to fetch the utxo of an individual input in m_inputs. Each caller fetches the input at m_input_head and increments it, so each call will fetch the next input in the queue. Fetch coins from the m_inputs vector in FetchCoinFromBase by scanning all inputs until we discover the input with the correct outpoint. This is designed deliberately so multiple threads can call ProcessInput independently. Co-authored-by: l0rinc <pap.lorinc@gmail.com> Co-authored-by: Hodlinator <172445034+hodlinator@users.noreply.github.com>
Inputs spending outputs of an earlier transaction in the same block won't be in the cache or the db. They also won't be requested by FetchCoinFromBase, so we can filter them out to not waste time trying to fetch them. Build an unordered set of seen txids while flattening m_inputs and skip any prevout whose hash is already in the set. Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Provides a worst-case upper bound on the number of inputs that can fit in a block, so callers (e.g. parallel input prefetching) can pre-allocate stable storage and rule out reallocation of per-input state. Cherry-picked from PR bitcoin#9938 (Lock-Free CheckQueue), with MAX_TXINS_PER_BLOCK renamed to MAX_INPUTS_PER_BLOCK to match the call site. Co-authored-by: Jeremy Rubin <jeremy.l.rubin@gmail.com>
Prepares for ProcessInput to be called from multiple threads. This flag acts as a memory fence around InputToFetch::coin. There is no lock guarding reads and writes of the coin field. Instead we use the flag's release/acquire semantics to ensure that when the main thread reads the coin it will have happened after a worker thread has finished writing it. Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Prepares for ProcessInput to be called from multiple threads. ProcessInput reads from base. For ProcessInput to be safe to call in parallel on separate threads, it must not be mutated. Flush, Sync, and SetBackend can modify base, so we override these and StopFetching before calling the base class. Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Add a configuration option for the number of worker threads used for parallel UTXO input fetching during block connection. Default is 4 threads, max is 16, 0 disables parallel fetching.
Prepares for ProcessInput to be called from multiple threads. Introduce a ThreadPool shared pointer to CoinsViewOverlay. A pool managed externally can be passed in the constructor. A global thread pool is used in fuzz harnesses since iterations can happen faster than the OS can create and tear down thread pools. This can cause a memory leak when fuzzing. Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Leverages the thread pool to fetch inputs on multiple threads, while the overlay serves inputs on the main thread. This is a performance improvement over blocking the main thread to fetch inputs. Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Co-authored-by: l0rinc <pap.lorinc@gmail.com>
Co-authored-by: l0rinc <pap.lorinc@gmail.com> Co-authored-by: sedited <seb.kung@gmail.com>
WriteCoinsViewEntry's local map allocates coins via the test resource and relies on FreeAllCoins() running after BatchWrite returns. When BatchWrite throws (e.g. EX_FRESH_MISAPPLIED in ccoins_write), that cleanup is skipped and the temp map is destroyed with non-null coin pointers, which trips the ~CCoinsCacheEntry assertion that coin == nullptr. Catch and rethrow so the coins are always released. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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