lbcd/wire/msgnotfound.go
Dave Collins 2adfb3b56a wire: Reduce allocs with contiguous slices.
The current code involves a ton of small allocations which is harsh on
the garbage collector and in turn causes a lot of addition runtime
overhead both in terms of additional memory and processing time.

In order to improve the situation, this drasticially reduces the number
of allocations by creating contiguous slices of objects and
deserializing into them.  Since the final data structures consist of
slices of pointers to the objects, they are constructed by pointing them
into the appropriate offset of the contiguous slice.

This could be improved upon even further by converting all of the data
structures provided the wire package to be slices of contiguous objects
directly, however that would be a major breaking API change and would
end up requiring updating a lot more code in every caller.  I do think
that ultimately the API should be changed, but the changes in this
commit already makes a massive difference and it doesn't require
touching any of the callers, so it is a good place to begin.

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
-----------------------------------------------------------
DeserializeTxLarge     16715          11146          -33.32%
DecodeGetHeaders       501            2              -99.60%
DecodeHeaders          2001           2              -99.90%
DecodeGetBlocks        501            2              -99.60%
DecodeAddr             3001           2002           -33.29%
DecodeInv              50003          3              -99.99%
DecodeNotFound         50002          3              -99.99%
DecodeMerkleBlock      107            3              -97.20%
2016-06-03 17:08:31 -05:00

110 lines
3.2 KiB
Go

// Copyright (c) 2013-2015 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package wire
import (
"fmt"
"io"
)
// MsgNotFound defines a bitcoin notfound message which is sent in response to
// a getdata message if any of the requested data in not available on the peer.
// Each message is limited to a maximum number of inventory vectors, which is
// currently 50,000.
//
// Use the AddInvVect function to build up the list of inventory vectors when
// sending a notfound message to another peer.
type MsgNotFound struct {
InvList []*InvVect
}
// AddInvVect adds an inventory vector to the message.
func (msg *MsgNotFound) AddInvVect(iv *InvVect) error {
if len(msg.InvList)+1 > MaxInvPerMsg {
str := fmt.Sprintf("too many invvect in message [max %v]",
MaxInvPerMsg)
return messageError("MsgNotFound.AddInvVect", str)
}
msg.InvList = append(msg.InvList, iv)
return nil
}
// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgNotFound) BtcDecode(r io.Reader, pver uint32) error {
count, err := ReadVarInt(r, pver)
if err != nil {
return err
}
// Limit to max inventory vectors per message.
if count > MaxInvPerMsg {
str := fmt.Sprintf("too many invvect in message [%v]", count)
return messageError("MsgNotFound.BtcDecode", str)
}
// Create a contiguous slice of inventory vectors to deserialize into in
// order to reduce the number of allocations.
invList := make([]InvVect, count)
msg.InvList = make([]*InvVect, 0, count)
for i := uint64(0); i < count; i++ {
iv := &invList[i]
err := readInvVect(r, pver, iv)
if err != nil {
return err
}
msg.AddInvVect(iv)
}
return nil
}
// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgNotFound) BtcEncode(w io.Writer, pver uint32) error {
// Limit to max inventory vectors per message.
count := len(msg.InvList)
if count > MaxInvPerMsg {
str := fmt.Sprintf("too many invvect in message [%v]", count)
return messageError("MsgNotFound.BtcEncode", str)
}
err := WriteVarInt(w, pver, uint64(count))
if err != nil {
return err
}
for _, iv := range msg.InvList {
err := writeInvVect(w, pver, iv)
if err != nil {
return err
}
}
return nil
}
// Command returns the protocol command string for the message. This is part
// of the Message interface implementation.
func (msg *MsgNotFound) Command() string {
return CmdNotFound
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgNotFound) MaxPayloadLength(pver uint32) uint32 {
// Max var int 9 bytes + max InvVects at 36 bytes each.
// Num inventory vectors (varInt) + max allowed inventory vectors.
return MaxVarIntPayload + (MaxInvPerMsg * maxInvVectPayload)
}
// NewMsgNotFound returns a new bitcoin notfound message that conforms to the
// Message interface. See MsgNotFound for details.
func NewMsgNotFound() *MsgNotFound {
return &MsgNotFound{
InvList: make([]*InvVect, 0, defaultInvListAlloc),
}
}