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Merge bitcoin/bitcoin#33078: kernel: improve BlockChecked ownership semantics

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1d9f1cb4bd kernel: improve BlockChecked ownership semantics (stickies-v)
9ba1fff29e kernel: refactor: ConnectTip to pass block pointer by value (stickies-v)

Pull request description:

  Subscribers to the BlockChecked validation interface event may need access to the block outside of the callback scope. Currently, this is only possible by copying the block, which makes exposing this validation interface event publicly either cumbersome or with significant copy overhead.

  By using shared_ptr, we make the shared ownership explicit and allow users to safely use the block outside of the callback scope. By using a const-ref shared_ptr, no atomic reference count cost is incurred if a subscriber does not require block ownership.

  For example: in  #30595, this would allow us to drop the `kernel_BlockPointer` handle entirely, and generalize everything into `kernel_Block`. This PoC is implemented in https://github.com/stickies-v/bitcoin/commits/kernel/remove-blockpointer/.

  ---

  ### Performance

  I have added a benchmark in a [separate branch](https://github.com/stickies-v/bitcoin/commits/2025-07/validation-interface-ownership-benched/), to ensure this change does not lead to a problematic performance regression. Since most of the overhead comes from the subscribers, I have added scenarios for `One`, `Two`, and `Ten` subscribers. From these results, it appears there is no meaningful performance difference on my machine.

  When `BlockChecked()` takes a `const CBlock&` reference _(master)_:
  |               ns/op |                op/s |    err% |     total | benchmark
  |--------------------:|--------------------:|--------:|----------:|:----------
  |              170.09 |        5,879,308.26 |    0.3% |      0.01 | `BlockCheckedOne`
  |            1,603.95 |          623,460.10 |    0.5% |      0.01 | `BlockCheckedTen`
  |              336.00 |        2,976,173.37 |    1.1% |      0.01 | `BlockCheckedTwo`

  When `BlockChecked()` takes a `const std::shared_ptr<const CBlock>&` _(this PR)_:
  |               ns/op |                op/s |    err% |     total | benchmark
  |--------------------:|--------------------:|--------:|----------:|:----------
  |              172.20 |        5,807,155.33 |    0.1% |      0.01 | `BlockCheckedOne`
  |            1,596.79 |          626,254.52 |    0.0% |      0.01 | `BlockCheckedTen`
  |              333.38 |        2,999,603.17 |    0.3% |      0.01 | `BlockCheckedTwo`

ACKs for top commit:
  achow101:
    ACK 1d9f1cb4bd
  w0xlt:
    reACK 1d9f1cb4bd
  ryanofsky:
    Code review ACK 1d9f1cb4bd. These all seem like simple changes that make sense
  TheCharlatan:
    ACK 1d9f1cb4bd
  yuvicc:
    Code Review ACK 1d9f1cb4bd

Tree-SHA512: 7ed0cccb7883dbb1885917ef749ab7cae5d60ee803b7e3145b2954d885e81ba8c9d5ab1edb9694ce6b308235c621094c029024eaf99f1aab1b47311c40958095
This commit is contained in:
Ava Chow
2025-08-20 10:45:36 -07:00
parent bc797d2271 1d9f1cb4bd
commit 04c115dfde
9 changed files with 42 additions and 33 deletions
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26
src/validation.cpp
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@@ -3108,7 +3108,12 @@ public:
*
* The block is added to connectTrace if connection succeeds.
*/
bool Chainstate::ConnectTip(BlockValidationState& state, CBlockIndex* pindexNew, const std::shared_ptr<const CBlock>& pblock, ConnectTrace& connectTrace, DisconnectedBlockTransactions& disconnectpool)
bool Chainstate::ConnectTip(
BlockValidationState& state,
CBlockIndex* pindexNew,
std::shared_ptr<const CBlock> block_to_connect,
ConnectTrace& connectTrace,
DisconnectedBlockTransactions& disconnectpool)
{
AssertLockHeld(cs_main);
if (m_mempool) AssertLockHeld(m_mempool->cs);
@@ -3116,18 +3121,15 @@ bool Chainstate::ConnectTip(BlockValidationState& state, CBlockIndex* pindexNew,
assert(pindexNew->pprev == m_chain.Tip());
// Read block from disk.
const auto time_1{SteadyClock::now()};
std::shared_ptr<const CBlock> pthisBlock;
if (!pblock) {
if (!block_to_connect) {
std::shared_ptr<CBlock> pblockNew = std::make_shared<CBlock>();
if (!m_blockman.ReadBlock(*pblockNew, *pindexNew)) {
return FatalError(m_chainman.GetNotifications(), state, _("Failed to read block."));
}
pthisBlock = pblockNew;
block_to_connect = std::move(pblockNew);
} else {
LogDebug(BCLog::BENCH, " - Using cached block\n");
pthisBlock = pblock;
}
const CBlock& blockConnecting = *pthisBlock;
// Apply the block atomically to the chain state.
const auto time_2{SteadyClock::now()};
SteadyClock::time_point time_3;
@@ -3137,9 +3139,9 @@ bool Chainstate::ConnectTip(BlockValidationState& state, CBlockIndex* pindexNew,
Ticks<MillisecondsDouble>(time_2 - time_1));
{
CCoinsViewCache view(&CoinsTip());
bool rv = ConnectBlock(blockConnecting, state, pindexNew, view);
bool rv = ConnectBlock(*block_to_connect, state, pindexNew, view);
if (m_chainman.m_options.signals) {
m_chainman.m_options.signals->BlockChecked(blockConnecting, state);
m_chainman.m_options.signals->BlockChecked(block_to_connect, state);
}
if (!rv) {
if (state.IsInvalid())
@@ -3175,8 +3177,8 @@ bool Chainstate::ConnectTip(BlockValidationState& state, CBlockIndex* pindexNew,
Ticks<MillisecondsDouble>(m_chainman.time_chainstate) / m_chainman.num_blocks_total);
// Remove conflicting transactions from the mempool.;
if (m_mempool) {
m_mempool->removeForBlock(blockConnecting.vtx, pindexNew->nHeight);
disconnectpool.removeForBlock(blockConnecting.vtx);
m_mempool->removeForBlock(block_to_connect->vtx, pindexNew->nHeight);
disconnectpool.removeForBlock(block_to_connect->vtx);
}
// Update m_chain & related variables.
m_chain.SetTip(*pindexNew);
@@ -3202,7 +3204,7 @@ bool Chainstate::ConnectTip(BlockValidationState& state, CBlockIndex* pindexNew,
m_chainman.MaybeCompleteSnapshotValidation();
}
connectTrace.BlockConnected(pindexNew, std::move(pthisBlock));
connectTrace.BlockConnected(pindexNew, std::move(block_to_connect));
return true;
}
@@ -4515,7 +4517,7 @@ bool ChainstateManager::ProcessNewBlock(const std::shared_ptr<const CBlock>& blo
}
if (!ret) {
if (m_options.signals) {
m_options.signals->BlockChecked(*block, state);
m_options.signals->BlockChecked(block, state);
}
LogError("%s: AcceptBlock FAILED (%s)\n", __func__, state.ToString());
return false;