# Gavin Andresen
# 2012-11-02 18:10:52
# https://bitcointalk.org/index.php?topic=122079.msg1313405#msg1313405

The relevant settings and their default values for recent versions of bitcoind are: @p{par}


Code:
Maximum size, in bytes, of blocks you create: @p{brk}
blockmaxsize=250000 @p{par}

How many bytes of the block should be dedicated to high-priority transactions,                                                                                                  @p{brk}
included regardless of the fees they pay                                                                                                                                  @p{brk}
blockprioritysize=27000 @p{par}

Minimum block size you want to create; block will be filled with free transactions                                                                                        @p{brk}
until there are no more or the block reaches this size:                                                                                                                   @p{brk}
blockminsize=0 @p{par}

Fee-per-kilobyte amount (in BTC) considered the same as "free"                                                                                                                     @p{brk}
Be careful setting this: if you set it to zero then                                                                                                                       @p{brk}
a transaction spammer can cheaply fill blocks using                                                                                                                       @p{brk}
1-satoshi-fee transactions. It should be set above the real                                                                                                               @p{brk}
cost to you of processing a transaction.                                                                                                                                  @p{brk}
mintxfee=0.0005 @p{brk}

 @p{brk}
So if you set blockprioritysize=0, you will only accept fee-paying transactions. @p{par}

If you only want to accept 500 or so transactions, set the blocksize to 500 * average transaction size (400 bytes or so) = 200000 @p{par}

The rules for filling up the block are: @p{par}

First, take the highest priority transactions (regardless of fee) and fill up the block to blockprioritysize.  (if blockprioritysize is zero, then this step does not apply) @p{par}

Then, take the highest fee-per-kilobyte transactions and continue filling the block until either you run out of transactions with a fee-per-kilobyte greater than mintxfee or the block would be larger than blockmaxsize. @p{par}

Finally: the rules are likely to change again fairly soon so that groups of related transactions are considered together ("child pays for parent", so customers can send zero-fee transactions to merchants, who can create a child transaction with a fee when they need the transaction to be confirmed). @p{brk}