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diff --git a/doc/release-notes.md b/doc/release-notes.md index 240e132a83..b251e8355a 100644 --- a/doc/release-notes.md +++ b/doc/release-notes.md @@ -146,6 +146,68 @@ HD wallets are incompatible with older versions of Bitcoin Core. [Pull request](https://github.com/bitcoin/bitcoin/pull/8035/files), [BIP 32](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki) +Segregated Witness +------------------ + +The code preparations for Segregated Witness ("segwit"), as described in [BIP +141](https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki), [BIP +143](https://github.com/bitcoin/bips/blob/master/bip-0143.mediawiki), [BIP +144](https://github.com/bitcoin/bips/blob/master/bip-0144.mediawiki), and [BIP +145](https://github.com/bitcoin/bips/blob/master/bip-0145.mediawiki) are +finished and included in this release. However, BIP 141 does not yet specify +activation parameters on mainnet, and so this release does not support segwit +use on mainnet. Testnet use is supported, and after BIP 141 is updated with +proposed parameters, a future release of Bitcoin Core is expected that +implements those parameters for mainnet. + +Furthermore, because segwit activation is not yet specified for mainnet, +version 0.13.0 will behave similarly as other pre-segwit releases even after a +future activation of BIP 141 on the network. Upgrading from 0.13.0 will be +required in order to utilize segwit-related features on mainnet (such as signal +BIP 141 activation, mine segwit blocks, fully validate segwit blocks, relay +segwit blocks to other segwit nodes, and use segwit transactions in the +wallet, etc). + +Mining transaction selection ("Child Pays For Parent") +------------------------------------------------------ + +The mining transaction selection algorithm has been replaced with an algorithm +that selects transactions based on their feerate inclusive of unconfirmed +ancestor transactions. This means that a low-fee transaction can become more +likely to be selected if a high-fee transaction that spends its outputs is +relayed. + +With this change, the `-blockminsize` command line option has been removed. + +The command line option `-blockmaxsize` remains an option to specify the +maximum number of serialized bytes in a generated block. In addition, the new +command line option `-blockmaxweight` has been added, which specifies the +maximum "block weight" of a generated block, as defined by [BIP 141 (Segregated +Witness)] (https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki). + +In preparation for Segregated Witness, the mining algorithm has been modified +to optimize transaction selection for a given block weight, rather than a given +number of serialized bytes in a block. In this release, transaction selection +is unaffected by this distinction (as BIP 141 activation is not supported on +mainnet in this release, see above), but in future releases and after BIP 141 +activation, these calculations would be expected to differ. + +For optimal runtime performance, miners using this release should specify +`-blockmaxweight` on the command line, and not specify `-blockmaxsize`. +Additionally (or only) specifying `-blockmaxsize`, or relying on default +settings for both, may result in performance degradation, as the logic to +support `-blockmaxsize` performs additional computation to ensure that +constraint is met. (Note that for mainnet, in this release, the equivalent +parameter for `-blockmaxweight` would be four times the desired +`-blockmaxsize`. See [BIP 141] +(https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki) for additional +details.) + +In the future, the `-blockmaxsize` option may be removed, as block creation is +no longer optimized for this metric. Feedback is requested on whether to +deprecate or keep this command line option in future releases. + + Removal of internal miner -------------------------- |