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⚡ Bolt: Optimize eBPF event parsing #182

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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
## 2025-05-19 - Manual Binary Parsing vs binary.Read
**Learning:** `binary.Read` uses reflection and can be significantly slower (orders of magnitude) than manual parsing using `binary.LittleEndian.UintXX`, especially in hot loops like eBPF event processing. Additionally, `binary.Read` forces full struct allocation and copying, which is wasteful for large structs where only a part of the data is needed (e.g. variable length payloads).
**Action:** For high-frequency binary data deserialization, prefer manual parsing with `encoding/binary` and explicit bounds checking.
177 changes: 89 additions & 88 deletions ebpftracer/tracer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -355,52 +355,6 @@ func (t EventReason) String() string {
return "unknown: " + strconv.Itoa(int(t))
}

type procEvent struct {
Type EventType
Pid uint32
Reason uint32
}

type tcpEvent struct {
Fd uint64
Timestamp uint64
Duration uint64
Type EventType
Pid uint32
BytesSent uint64
BytesReceived uint64
SPort uint16
DPort uint16
Aport uint16
SAddr [16]byte
DAddr [16]byte
AAddr [16]byte
}

type fileEvent struct {
Type EventType
Pid uint32
Fd uint64
Mnt uint64
Log uint64
}

type l7Event struct {
Fd uint64
ConnectionTimestamp uint64
Pid uint32
Status int32
Duration uint64
Protocol uint8
Method uint8
Padding uint16
StatementId uint32
PayloadSize uint64
ResponseSize uint64
Payload [4096]byte // Must match MAX_PAYLOAD_SIZE in eBPF
Response [4096]byte // Must match MAX_PAYLOAD_SIZE in eBPF
}

// HTTP response fragment event (must match eBPF struct)
type httpResponseFragment struct {
Fd uint64
Expand Down Expand Up @@ -468,78 +422,125 @@ func runEventsReader(name string, r *perf.Reader, ch chan<- Event, typ perfMapTy

switch typ {
case perfMapTypeL7Events:
v := &l7Event{}
data := rec.RawSample

if err := binary.Read(bytes.NewBuffer(data), binary.LittleEndian, v); err != nil {
klog.Warningln("failed to read l7 event:", err)
if len(data) < 56 {
klog.Warningln("l7 event too short")
continue
}
fd := binary.LittleEndian.Uint64(data[0:8])
timestamp := binary.LittleEndian.Uint64(data[8:16])
pid := binary.LittleEndian.Uint32(data[16:20])
status := int32(binary.LittleEndian.Uint32(data[20:24]))
duration := binary.LittleEndian.Uint64(data[24:32])
protocol := data[32]
method := data[33]
// padding 2 bytes
statementId := binary.LittleEndian.Uint32(data[36:40])
payloadSizeVal := binary.LittleEndian.Uint64(data[40:48])
responseSizeVal := binary.LittleEndian.Uint64(data[48:56])

const maxPayloadSize = 4096
payloadSize := int(payloadSizeVal)
if payloadSize > maxPayloadSize {
payloadSize = maxPayloadSize
}
responseSize := int(responseSizeVal)
if responseSize > maxPayloadSize {
responseSize = maxPayloadSize
}

// Extract payload data directly from the struct arrays
payloadSize := min(int(v.PayloadSize), len(v.Payload))
responseSize := min(int(v.ResponseSize), len(v.Response))
payloadStart := 56
responseStart := 56 + maxPayloadSize
if len(data) < responseStart+responseSize {
klog.Warningln("l7 event too short for payload/response")
continue
}

// Copy the actual data (preventing garbage from unused buffer space)
payloadData := make([]byte, payloadSize)
copy(payloadData, v.Payload[:payloadSize])
copy(payloadData, data[payloadStart:payloadStart+payloadSize])

responseData := make([]byte, responseSize)
copy(responseData, v.Response[:responseSize])
copy(responseData, data[responseStart:responseStart+responseSize])

req := &l7.RequestData{
Protocol: l7.Protocol(v.Protocol),
Status: l7.Status(v.Status),
Duration: time.Duration(v.Duration),
Method: l7.Method(v.Method),
StatementId: v.StatementId,
PayloadSize: v.PayloadSize,
ResponseSize: v.ResponseSize,
Protocol: l7.Protocol(protocol),
Status: l7.Status(status),
Duration: time.Duration(duration),
Method: l7.Method(method),
StatementId: statementId,
PayloadSize: payloadSizeVal,
ResponseSize: responseSizeVal,
Payload: payloadData,
Response: responseData,
}

event = Event{
Type: EventTypeL7Request,
Pid: v.Pid,
Fd: v.Fd,
Timestamp: v.ConnectionTimestamp,
Pid: pid,
Fd: fd,
Timestamp: timestamp,
L7Request: req,
}
case perfMapTypeFileEvents:
v := &fileEvent{}
if err := binary.Read(bytes.NewBuffer(rec.RawSample), binary.LittleEndian, v); err != nil {
klog.Warningln("failed to read file event:", err)
data := rec.RawSample
if len(data) < 32 {
klog.Warningln("file event too short")
continue
}
event = Event{Type: v.Type, Pid: v.Pid, Fd: v.Fd, Mnt: v.Mnt, Log: v.Log > 0}
typ := EventType(binary.LittleEndian.Uint32(data[0:4]))
pid := binary.LittleEndian.Uint32(data[4:8])
fd := binary.LittleEndian.Uint64(data[8:16])
mnt := binary.LittleEndian.Uint64(data[16:24])
logFlag := binary.LittleEndian.Uint64(data[24:32])

event = Event{Type: typ, Pid: pid, Fd: fd, Mnt: mnt, Log: logFlag > 0}
case perfMapTypeProcEvents:
v := &procEvent{}
if err := binary.Read(bytes.NewBuffer(rec.RawSample), binary.LittleEndian, v); err != nil {
klog.Warningln("failed to read proc event:", err)
data := rec.RawSample
if len(data) < 12 {
klog.Warningln("proc event too short")
continue
}
event = Event{Type: v.Type, Reason: EventReason(v.Reason), Pid: v.Pid}
typ := EventType(binary.LittleEndian.Uint32(data[0:4]))
pid := binary.LittleEndian.Uint32(data[4:8])
reason := binary.LittleEndian.Uint32(data[8:12])

event = Event{Type: typ, Reason: EventReason(reason), Pid: pid}
case perfMapTypeTCPEvents:
v := &tcpEvent{}
if err := binary.Read(bytes.NewBuffer(rec.RawSample), binary.LittleEndian, v); err != nil {
klog.Warningln("failed to read tcp event:", err)
data := rec.RawSample
if len(data) < 102 {
klog.Warningln("tcp event too short")
continue
}
fd := binary.LittleEndian.Uint64(data[0:8])
timestamp := binary.LittleEndian.Uint64(data[8:16])
duration := binary.LittleEndian.Uint64(data[16:24])
typ := EventType(binary.LittleEndian.Uint32(data[24:28]))
pid := binary.LittleEndian.Uint32(data[28:32])
bytesSent := binary.LittleEndian.Uint64(data[32:40])
bytesReceived := binary.LittleEndian.Uint64(data[40:48])
sPort := binary.LittleEndian.Uint16(data[48:50])
dPort := binary.LittleEndian.Uint16(data[50:52])
aPort := binary.LittleEndian.Uint16(data[52:54])

var sAddr, dAddr, aAddr [16]byte
copy(sAddr[:], data[54:70])
copy(dAddr[:], data[70:86])
copy(aAddr[:], data[86:102])

event = Event{
Type: v.Type,
Pid: v.Pid,
SrcAddr: ipPort(v.SAddr, v.SPort),
DstAddr: ipPort(v.DAddr, v.DPort),
ActualDstAddr: ipPort(v.AAddr, v.Aport),
Fd: v.Fd,
Timestamp: v.Timestamp,
Duration: time.Duration(v.Duration),
Type: typ,
Pid: pid,
SrcAddr: ipPort(sAddr, sPort),
DstAddr: ipPort(dAddr, dPort),
ActualDstAddr: ipPort(aAddr, aPort),
Fd: fd,
Timestamp: timestamp,
Duration: time.Duration(duration),
}
if v.Type == EventTypeConnectionClose {
if typ == EventTypeConnectionClose {
event.TrafficStats = &TrafficStats{
BytesSent: v.BytesSent,
BytesReceived: v.BytesReceived,
BytesSent: bytesSent,
BytesReceived: bytesReceived,
}
}
default:
Expand Down
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