Decred's serialized format for transactions split the 32-bit version
field into two 16-bit components such that the upper bits are used to
encode a serialization type and the lower 16 bits are the actual
transaction version.
Unfortunately, when this was done, the in-memory transaction struct was
not also updated to hide this complexity, which means that callers
currently have to understand and take special care when dealing with the
version field of the transaction.
Since the main purpose of the wire package is precisely to hide these
details, this remedies the situation by introducing a new field on the
in-memory transaction struct named SerType which houses the
serialization type and changes the Version field back to having the
desired semantics of actually being the real transaction version. Also,
since the maximum version can only be a 16-bit value, the Version field
has been changed to a uint16 to properly reflect this.
The serialization and deserialization functions now deal with properly
converting to and from these fields to the actual serialized format as
intended.
Finally, these changes also include a fairly significant amount of
related code cleanup and optimization along with some bug fixes in order
to allow the transaction version to be bumped as intended.
The following is an overview of all changes:
- Introduce new SerType field to MsgTx to specify the serialization type
- Change MsgTx.Version to a uint16 to properly reflect its maximum
allowed value
- Change the semantics of MsgTx.Version to be the actual transaction
version as intended
- Update all callers that had special code to deal with the previous
Version field semantics to use the new semantics
- Switch all of the code that deals with encoding and decoding the
serialized version field to use more efficient masks and shifts
instead of binary writes into buffers which cause allocations
- Correct several issues that would prevent producing expected
serializations for transactions with actual transaction versions that
are not 1
- Simplify the various serialize functions to use a single func which
accepts the serialization type to reduce code duplication
- Make serialization type switch usage more consistent with the rest of
the code base
- Update the utxoview and related code to use uint16s for the
transaction version as well since it should not care about the
serialization type due to using its own
- Make code more consistent in how it uses bytes.Buffer
- Clean up several of the comments regarding hashes and add some new
comments to better describe the serialization types
Contains the following commits:
- 711f33450c
- b6b1e55d1e
- Reverted because Travis is already at a more recent version
- bd4e64d1d4
Also, the merge commit contains the necessary decred-specific
alterations, converts all other references to sha to hash to keep with
the spirit of the merged commits, and various other cleanup intended to
bring the code bases more in line with one another.
Bump block version and add stake version to wire. Currently
StakeVersions are unused and once the enforcement logic goes in the
versions will bump again.
This fixes#435
This commit is the first stage of several that are planned to convert
the blockchain package into a concurrent safe package that will
ultimately allow support for multi-peer download and concurrent chain
processing. The goal is to update btcd proper after each step so it can
take advantage of the enhancements as they are developed.
In addition to the aforementioned benefit, this staged approach has been
chosen since it is absolutely critical to maintain consensus.
Separating the changes into several stages makes it easier for reviewers
to logically follow what is happening and therefore helps prevent
consensus bugs. Naturally there are significant automated tests to help
prevent consensus issues as well.
The main focus of this stage is to convert the blockchain package to use
the new database interface and implement the chain-related functionality
which it no longer handles. It also aims to improve efficiency in
various areas by making use of the new database and chain capabilities.
The following is an overview of the chain changes:
- Update to use the new database interface
- Add chain-related functionality that the old database used to handle
- Main chain structure and state
- Transaction spend tracking
- Implement a new pruned unspent transaction output (utxo) set
- Provides efficient direct access to the unspent transaction outputs
- Uses a domain specific compression algorithm that understands the
standard transaction scripts in order to significantly compress them
- Removes reliance on the transaction index and paves the way toward
eventually enabling block pruning
- Modify the New function to accept a Config struct instead of
inidividual parameters
- Replace the old TxStore type with a new UtxoViewpoint type that makes
use of the new pruned utxo set
- Convert code to treat the new UtxoViewpoint as a rolling view that is
used between connects and disconnects to improve efficiency
- Make best chain state always set when the chain instance is created
- Remove now unnecessary logic for dealing with unset best state
- Make all exported functions concurrent safe
- Currently using a single chain state lock as it provides a straight
forward and easy to review path forward however this can be improved
with more fine grained locking
- Optimize various cases where full blocks were being loaded when only
the header is needed to help reduce the I/O load
- Add the ability for callers to get a snapshot of the current best
chain stats in a concurrent safe fashion
- Does not block callers while new blocks are being processed
- Make error messages that reference transaction outputs consistently
use <transaction hash>:<output index>
- Introduce a new AssertError type an convert internal consistency
checks to use it
- Update tests and examples to reflect the changes
- Add a full suite of tests to ensure correct functionality of the new
code
The following is an overview of the btcd changes:
- Update to use the new database and chain interfaces
- Temporarily remove all code related to the transaction index
- Temporarily remove all code related to the address index
- Convert all code that uses transaction stores to use the new utxo
view
- Rework several calls that required the block manager for safe
concurrency to use the chain package directly now that it is
concurrent safe
- Change all calls to obtain the best hash to use the new best state
snapshot capability from the chain package
- Remove workaround for limits on fetching height ranges since the new
database interface no longer imposes them
- Correct the gettxout RPC handler to return the best chain hash as
opposed the hash the txout was found in
- Optimize various RPC handlers:
- Change several of the RPC handlers to use the new chain snapshot
capability to avoid needlessly loading data
- Update several handlers to use new functionality to avoid accessing
the block manager so they are able to return the data without
blocking when the server is busy processing blocks
- Update non-verbose getblock to avoid deserialization and
serialization overhead
- Update getblockheader to request the block height directly from
chain and only load the header
- Update getdifficulty to use the new cached data from chain
- Update getmininginfo to use the new cached data from chain
- Update non-verbose getrawtransaction to avoid deserialization and
serialization overhead
- Update gettxout to use the new utxo store versus loading
full transactions using the transaction index
The following is an overview of the utility changes:
- Update addblock to use the new database and chain interfaces
- Update findcheckpoint to use the new database and chain interfaces
- Remove the dropafter utility which is no longer supported
NOTE: The transaction index and address index will be reimplemented in
another commit.
This is mostly a backport of some of the same modifications made in
Decred along with a few additional things cleaned up. In particular,
this updates the code to make use of the new chainhash package.
Also, since this required API changes anyways and the hash algorithm is
no longer tied specifically to SHA, all other functions throughout the
code base which had "Sha" in their name have been changed to Hash so
they are not incorrectly implying the hash algorithm.
The following is an overview of the changes:
- Remove the wire.ShaHash type
- Update all references to wire.ShaHash to the new chainhash.Hash type
- Rename the following functions and update all references:
- wire.BlockHeader.BlockSha -> BlockHash
- wire.MsgBlock.BlockSha -> BlockHash
- wire.MsgBlock.TxShas -> TxHashes
- wire.MsgTx.TxSha -> TxHash
- blockchain.ShaHashToBig -> HashToBig
- peer.ShaFunc -> peer.HashFunc
- Rename all variables that included sha in their name to include hash
instead
- Update for function name changes in other dependent packages such as
btcutil
- Update copyright dates on all modified files
- Update glide.lock file to use the required version of btcutil
Putting the test code in the same package makes it easier for forks
since they don't have to change the import paths as much and it also
gets rid of the need for internal_test.go to bridge.
This same thing should probably be done for the majority of the code
base.
This commit drastically reduces the number of allocations needed to
deserialize a transaction and its scripts by using the combination of a
free list for initially deserializing the individual scripts along with
copying them into a single contiguous byte slice after the final size is
known and modifying each script in the transaction to point to its
location within the contiguous blob.
The end result is only a single allocation that holds all of the scripts
for a transaction regardless of the total number of scripts it has.
The script free list allows a maximum of 12,500 items with each buffer
being 512 bytes. This implies it will have a peak usage of 6.1MB. The
values were chosen based on profiling data and a desire to allow at
least 100 scripts per transaction to be simultaneously deserialized by
125 peers.
Also, while optimizing, decode directly into the existing previous
outpoint structure of each transaction input in order to avoid the extra
allocation per input that is otherwise caused when the local escapes to
the heap.
The following is a before and after comparison of the allocations
with the benchmarks that did not change removed:
benchmark old allocs new allocs delta
-----------------------------------------------------------
ReadTxOut 1 0 -100.00%
ReadTxIn 2 0 -100.00%
DeserializeTxSmall 7 5 -28.57%
DeserializeTxLarge 11146 6 -99.95%
Contains the following upstream commits:
- f45db028db
- This commit was already cherry picked and is a NOOP
- f4d551c08d
- This commit was already cherry picked and is a NOOP
- c17ff82061
This adds decode benchmarks for several of the messages that profiling
has identified to cause a lot of allocations in addition to those that
already exist. By adding these benchmarks, it makes it easier to get
allocation and speed statistics which can in turn be used to compare
future improvements.
The following bencharmarks have been added:
DecodeGetHeaders, DecodeHeaders, DecodeGetBlocks, DecodeAddr, DecodeInv,
DecodeNotFound, and DecodeMerkleBlock
For reference, here is the benchmark data as of this commit.
DecodeGetHeaders 93261 ns/op 24120 B/op 1004 allocs/op
DecodeHeaders 2071263 ns/op 368399 B/op 18002 allocs/op
DecodeGetBlocks 92486 ns/op 24120 B/op 1004 allocs/op
DecodeAddr 850608 ns/op 136202 B/op 9002 allocs/op
DecodeInv 17107172 ns/op 3601447 B/op 150004 allocs/op
DecodeNotFound 17522225 ns/op 3601444 B/op 150004 allocs/op
DecodeMerkleBlock 21062 ns/op 5192 B/op 222 allocs/op
This modifies the benchmarks in the wire package to avoid creating a new
reader for each iteration. This is useful since it means that showing
the memory allocations will only show the function under test instead of
the allocation for the benchmark setup as well.
The following is a before and after comparison of the allocations
with the benchmarks that did not change removed:
benchmark old allocs new allocs delta
------------------------------------------------------------
ReadVarInt1 2 1 -50.00%
ReadVarInt3 2 1 -50.00%
ReadVarInt5 2 1 -50.00%
ReadVarInt9 2 1 -50.00%
ReadVarStr4 4 3 -25.00%
ReadVarStr10 4 3 -25.00%
ReadOutPoint 2 1 -50.00%
ReadTxOut 4 3 -25.00%
ReadTxIn 6 5 -16.67%
DeserializeTxSmall 16 15 -6.25%
DeserializeTxLarge 33430 33428 -0.01%
ReadBlockHeader 8 7 -12.50%
This adds a benchmark for deserializing a large transaction that is
often referred to as the megatransaction since it is the largest Bitcoin
transaction mined to date. It consists of 5569 inputs and 1 output and
its hash is:
bb41a757f405890fb0f5856228e23b715702d714d59bf2b1feb70d8b2b4e3e08.
This is being done so there is a benchmark that tests more of a
worst-case scenario which is a better candidate for identifying and
testing improvements.
The following benchmark results shows the how much more intensive this
transaction is over the existing mock transaction:
DeserializeTxSmall 1000000 1751 ns/op 376 B/op 16 allocs/op
DeserializeTxLarge 300 5093980 ns/op 1672829 B/op 33430 allocs/op
This commit exports the ReadVarString and WriteVarString functions so
they are available for callers to use.
A variable length string is encoded as a variable length integer
containing the length of the string followed by the bytes that represent
the string itself.
This commit exports the ReadVarString and WriteVarString functions so
they are available for callers to use.
A variable length string is encoded as a variable length integer
containing the length of the string followed by the bytes that represent
the string itself.
This commit adds a new function which is similar to the DoubleSha256
function except it returns a ShaHash copy instead of a byte slice. It
also adds a new benchmark for it.
This can be a slight optimization in certain cases where the caller
ultimately wants a ShaHash since it can avoid a heap allocation and
additional copy to convert the result to a ShaHash (the function simply
performs a type cast against the returned array which is not possible
against a []byte).
existing: DoubleSha256 500000 3081 ns/op 32 B/op 1 allocs/op
new: DoubleSha256SH 500000 2939 ns/op 0 B/op 0 allocs/op
The hashing functions for blocks and transactions have also been updated
to make use of the new function since they directly return the ShaHash.
The transaction change in particular is quite useful since transactions
are frequently hashed and this change allows all of those hashes to avoid
an additional heap allocation.
This commit contains three classes of optimizations:
- Reducing the number of unnecessary hash copies
- Improve the performance of the DoubleSha256 function
- A couple of minor optimizations of the ShaHash functions
The first class is a result of the Bytes function on a ShaHash making a
copy of the bytes before returning them. It really should have been named
CloneBytes, but that would break the API now.
To address this, a comment has been added to the function which explicitly
calls out the copy behavior. In addition, all call sites of .Bytes on a
ShaHash in the code base have been updated to simply slice the array when
a copy is not needed. This saves a significant amount of data copying.
The second optimization modifies the DoubleSha256 function to directly use
fastsha256.Sum256 instead of the hasher interface. This reduces the
number of allocations needed. A benchmark for the function has been added
as well.
old: BenchmarkDoubleSha256 500000 3691 ns/op 192 B/op 3 allocs/op
new: BenchmarkDoubleSha256 500000 3081 ns/op 32 B/op 1 allocs/op
The final optimizations are for the ShaHash IsEqual and SetBytes functions
which have been modified to make use of the fact the type is an array and
remove an unneeded subslice.
This commit contains the entire btcwire repository along with several
changes needed to move all of the files into the wire directory in
order to prepare it for merging. This does NOT update btcd or any of the
other packages to use the new location as that will be done separately.
- All import paths in the old btcwire test files have been changed to the
new location
- All references to btcwire as the package name have been chagned to
wire
- The coveralls badge has been removed since it unfortunately doesn't
support coverage of sub-packages
This is ongoing work toward #214.
