The mempool clusters and linearization permit sorting the mempool topologically
without making use of ancestor counts (as long as the graph is not oversized).
Co-authored-by: Pieter Wuille <pieter@wuille.net>
Previously, transaction batches were first sorted by ancestor count and then
feerate, to ensure transactions are announced in a topologically valid order,
while prioritizing higher feerate transactions. Ancestor count is a crude
topological sort criteria, so replace this with linearization order so that the
highest feerate transactions (as would be observed by the mining algorithm) are
relayed before lower feerate ones, in a topologically valid way.
This also fixes a test that only worked due to the ancestor-count-based sort
order.
With a total ordering on mempool transactions, we are now able to calculate a
transaction's mining score at all times. Use this to improve the RBF logic:
- we no longer enforce a "no new unconfirmed parents" rule
- we now require that the mempool's feerate diagram must improve in order
to accept a replacement
- the topology restrictions for conflicts in the package rbf setting have been
eliminated
Revert the temporary change to mempool_ephemeral_dust.py that were previously
made due to RBF validation checks being reordered.
Co-authored-by: Gregory Sanders <gsanders87@gmail.com>, glozow <gloriajzhao@gmail.com>
Rather than evicting the transactions with the lowest descendant feerate,
instead evict transactions that have the lowest chunk feerate.
Once mining is implemented based on choosing transactions with highest chunk
feerate (see next commit), mining and eviction will be opposites, so that we
will evict the transactions that would be mined last.
Include an adjustment to mempool_tests.cpp due to the additional memory used by
txgraph.
Includes a temporary change to the mempool_ephemeral_dust.py functional test,
due to validation checks being reordered. This change will revert once the RBF
rules are changed in a later commit.
Simplifies `m_tx_inventory_to_send` a bit by making it a set of Wtxids.
Wtxid relay is prevalent throughout the network, so the complexity of
dealing with a GenTxid in this data structure isn't necessary.
For peers that aren't wtxid relay, the txid is now retrieved from our
mempool entry when the inv is constructed.
During Initial Block Download, the mempool is usually empty, but `CTxMemPool::removeForBlock` is still called for every connected block where we:
* iterate over every transaction in the block even though none will be found in the empty `mapTx`, always leaving `txs_removed_for_block` empty...
* which is pre-allocated regardless with 40 bytes * vtx.size(), even though it will always remain empty.
This change introduces a minor performance optimization by only executing the loop if any of the core mempool maps have any contents.
The call to `MempoolTransactionsRemovedForBlock` and the updates to the rolling fee logic remain unchanged.
The `removeForBlock` was also updated stylistically to match the surrounding methods and a clarification was added to clarify that it affects fee estimation as well.
a60f863d3e276534444571282f432b913d3967db scripted-diff: Replace GenTxidVariant with GenTxid (marcofleon)
c8ba1995986323cd9e76097acc1f15eed7c60943 Remove old GenTxid class (marcofleon)
072a198ea4bc9f1e8449cd31e55d397b75ce4ad5 Convert remaining instances of GenTxid to GenTxidVariant (marcofleon)
1b528391c79497ae19f7e481439e350533c7cd1a Convert `txrequest` to GenTxidVariant (marcofleon)
bde4579b0780aa3754af35beffbcfeb31f28045b Convert `txdownloadman_impl` to GenTxidVariant (marcofleon)
c876a892ec0b04851bea0a688d7681b6aaca4cb7 Replace GenTxid with Txid/Wtxid overloads in `txmempool` (marcofleon)
de858ce2bea83c53635dee9a49c8c273a12440dd move-only: make GetInfo a private CTxMemPool member (stickies-v)
eee473d9f3019a0ea4ebbc9c41781813ad574a86 Convert `CompareInvMempoolOrder` to GenTxidVariant (marcofleon)
243553d59071f3e43a42f3809706790495b17ffc refactor: replace get_iter_from_wtxid with GetIter(const Wtxid&) (stickies-v)
fcf92fd640eae60d1f601136a4e1c9de8ccb68b5 refactor: make CTxMemPool::GetIter strongly typed (marcofleon)
11d28f21bb8f0c3094934b3fef45871f73bb216a Implement GenTxid as a variant (marcofleon)
Pull request description:
Part of the [type safety refactor](https://github.com/bitcoin/bitcoin/pull/32189).
This PR changes the GenTxid class to a variant, which holds both Txids and Wtxids. This provides compile-time type safety and eliminates the manual type check (bool m_is_wtxid). Variables that can be either a Txid or a Wtxid are now using the new GenTxid variant, instead of uint256.
ACKs for top commit:
w0xlt:
ACK a60f863d3e
dergoegge:
Code review ACK a60f863d3e276534444571282f432b913d3967db
maflcko:
review ACK a60f863d3e276534444571282f432b913d3967db 🎽
theStack:
Code-review ACK a60f863d3e276534444571282f432b913d3967db
Tree-SHA512: da9b73b7bdffee2eb9281a409205519ac330d3336094d17681896703fbca8099608782c9c85801e388e4d90af5af8abf1f34931f57bbbe6e9674d802d6066047
Now that we are storing `CTxMemPool::CompareDepthAndScore` parameters using
`std::variant` we have no portable zero-overhead way of accessing them,
so use `std::visit` and drop `bool wtxid` in-parameter.
Co-authored-by: stickies-v <stickies-v@protonmail.com>
This allows adding a GetIter(const Wtxid&) overload in a next
commit, making it easier to visit this function from a variant.
Co-authored-by: stickies-v <stickies-v@protonmail.com>
Also explicitly check for txid equality rather than transaction equality as the
former is a tighter constraint if witness data is included when comparing the
full transactions.
Co-authored-by: glozow <gloriajzhao@gmail.com>
Rather than individually calling addUnchecked for each transaction added in a
changeset (after removing all the to-be-removed transactions), instead we can
take advantage of boost::multi_index's splicing features to extract and insert
entries directly from the staging multi_index into mapTx.
This has the immediate advantage of saving allocation overhead for mempool
entries which have already been allocated once. This also means that the memory
locations of mempool entries will not change when transactions go from staging
to the main mempool.
Additionally, eliminate addUnchecked and require all new transactions to enter
the mempool via a CTxMemPoolChangeSet.
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.
This new function takes the populated sets of
direct and all conflicts computed in the current
mempool, assuming the replacements are a single
chunk, and computes a diagram check.
The diagram check only works against cluster
sizes of 2 or less, and fails if it encounters
a different topology.
Co-authored-by: Suhas Daftuar <sdaftuar@chaincode.com>
This is done in preparation for the next two commits, where the
CMainSignals are de-globalized.
This avoids adding new constructor arguments to the ChainstateManager
and CTxMemPool classes over the next two commits.
This could also allow future tests that are only interested in the
internal behaviour of the classes to forgo instantiating the signals.
29029df5c700e6940c712028303761d91ae15847 [doc] v3 signaling in mempool-replacements.md (glozow)
e643ea795e4b6fea4a6bbb3d72870ee6a4c836b1 [fuzz] v3 transactions and sigop-adjusted vsize (glozow)
1fd16b5c62f54c7f4c60122acd65d852f63d1e8b [functional test] v3 transaction submission (glozow)
27c8786ba918a42c860e6a50eaee9fdf56d7c646 test framework: Add and use option for tx-version in MiniWallet methods (MarcoFalke)
9a1fea55b29fe025355b06b45e3d77d192acc635 [policy/validation] allow v3 transactions with certain restrictions (glozow)
eb8d5a2e7d939dd3ee683486e98702079e0dfcc0 [policy] add v3 policy rules (glozow)
9a29d470fbb62bbb27d517efeafe46ff03c25f54 [rpc] return full string for package_msg and package-error (glozow)
158623b8e0726dff7eae4288138f1710e727db9c [refactor] change Workspace::m_conflicts and adjacent funcs/structs to use Txid (glozow)
Pull request description:
See #27463 for overall package relay tracking.
Delving Bitcoin discussion thread: https://delvingbitcoin.org/t/v3-transaction-policy-for-anti-pinning/340
Delving Bitcoin discussion for LN usage: https://delvingbitcoin.org/t/lightning-transactions-with-v3-and-ephemeral-anchors/418
Rationale:
- There are various pinning problems with RBF and our general ancestor/descendant limits. These policies help mitigate many pinning attacks and make package RBF feasible (see #28984 which implements package RBF on top of this). I would focus the most here on Rule 3 pinning. [1][2]
- Switching to a cluster-based mempool (see #27677 and #28676) requires the removal of CPFP carve out, which applications depend on. V3 + package RBF + ephemeral anchors + 1-parent-1-child package relay provides an intermediate solution.
V3 policy is for "Priority Transactions." [3][4] It allows users to opt in to more restrictive topological limits for shared transactions, in exchange for the more robust fee-bumping abilities that offers. Even though we don't have cluster limits, we are able to treat these transactions as having as having a maximum cluster size of 2.
Immediate benefits:
- You can presign a transaction with 0 fees (not just 1sat/vB!) and add a fee-bump later.
- Rule 3 pinning is reduced by a significant amount, since the attacker can only attach a maximum of 1000vB to your shared transaction.
This also enables some other cool things (again see #27463 for overall roadmap):
- Ephemeral Anchors
- Package RBF for these 1-parent-1-child packages. That means e.g. a commitment tx + child can replace another commitment tx using the child's fees.
- We can transition to a "single anchor" universe without worrying about package limit pinning. So current users of CPFP carve out would have something else to use.
- We can switch to a cluster-based mempool [5] (#27677#28676), which removes CPFP carve out [6].
[1]: Original mailing list post and discussion about RBF pinning problems https://gist.github.com/glozow/25d9662c52453bd08b4b4b1d3783b9ff, https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-January/019817.html
[2]: A FAQ is "we need this for cluster mempool, but is this still necessary afterwards?" There are some pinning issues that are fixed here and not fully fixed in cluster mempool, so we will still want this or something similar afterward.
[3]: Mailing list post for v3 https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2022-September/020937.html
[4]: Original PR #25038 also contains a lot of the discussion
[5]: https://delvingbitcoin.org/t/an-overview-of-the-cluster-mempool-proposal/393/7
[6]: https://delvingbitcoin.org/t/an-overview-of-the-cluster-mempool-proposal/393#the-cpfp-carveout-rule-can-no-longer-be-supported-12
ACKs for top commit:
sdaftuar:
ACK 29029df5c700e6940c712028303761d91ae15847
achow101:
ACK 29029df5c700e6940c712028303761d91ae15847
instagibbs:
ACK 29029df5c700e6940c712028303761d91ae15847 modulo that
Tree-SHA512: 9664b078890cfdca2a146439f8835c9d9ab483f43b30af8c7cd6962f09aa557fb1ce7689d5e130a2ec142235dbc8f21213881baa75241c5881660f9008d68450
