xray_fdr_log_records.h revision 341825 
1//===-- xray_fdr_log_records.h  -------------------------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file is a part of XRay, a function call tracing system.
11//
12//===----------------------------------------------------------------------===//
13#ifndef XRAY_XRAY_FDR_LOG_RECORDS_H
14#define XRAY_XRAY_FDR_LOG_RECORDS_H
15
16enum class RecordType : uint8_t { Function, Metadata };
17
18// A MetadataRecord encodes the kind of record in its first byte, and have 15
19// additional bytes in the end to hold free-form data.
20struct alignas(16) MetadataRecord {
21  // A MetadataRecord must always have a type of 1.
22  /* RecordType */ uint8_t Type : 1;
23
24  // Each kind of record is represented as a 7-bit value (even though we use an
25  // unsigned 8-bit enum class to do so).
26  enum class RecordKinds : uint8_t {
27    NewBuffer,
28    EndOfBuffer,
29    NewCPUId,
30    TSCWrap,
31    WalltimeMarker,
32    CustomEventMarker,
33    CallArgument,
34    BufferExtents,
35    TypedEventMarker,
36    Pid,
37  };
38
39  // Use 7 bits to identify this record type.
40  /* RecordKinds */ uint8_t RecordKind : 7;
41  char Data[15];
42} __attribute__((packed));
43
44static_assert(sizeof(MetadataRecord) == 16, "Wrong size for MetadataRecord.");
45
46struct alignas(8) FunctionRecord {
47  // A FunctionRecord must always have a type of 0.
48  /* RecordType */ uint8_t Type : 1;
49  enum class RecordKinds {
50    FunctionEnter = 0x00,
51    FunctionExit = 0x01,
52    FunctionTailExit = 0x02,
53  };
54  /* RecordKinds */ uint8_t RecordKind : 3;
55
56  // We only use 28 bits of the function ID, so that we can use as few bytes as
57  // possible. This means we only support 2^28 (268,435,456) unique function ids
58  // in a single binary.
59  int FuncId : 28;
60
61  // We use another 4 bytes to hold the delta between the previous entry's TSC.
62  // In case we've found that the distance is greater than the allowable 32 bits
63  // (either because we are running in a different CPU and the TSC might be
64  // different then), we should use a MetadataRecord before this FunctionRecord
65  // that will contain the full TSC for that CPU, and keep this to 0.
66  uint32_t TSCDelta;
67} __attribute__((packed));
68
69static_assert(sizeof(FunctionRecord) == 8, "Wrong size for FunctionRecord.");
70
71#endif // XRAY_XRAY_FDR_LOG_RECORDS_H
72