matrixfurry.com
The open source OpenXR runtime
1#include <atomic>
2#include <assert.h>
3#include <errno.h>
4#include <linux/perf_event.h>
5#include <stdint.h>
6#include <string.h>
7#include <sys/ioctl.h>
8#include <sys/mman.h>
9#include <unistd.h>
10
11#include "TracyDebug.hpp"
12
13namespace tracy
14{
15
16class RingBuffer
17{
18public:
19 RingBuffer( unsigned int size, int fd, int id, int cpu = -1 )
20 : m_size( size )
21 , m_id( id )
22 , m_cpu( cpu )
23 , m_fd( fd )
24 {
25 const auto pageSize = uint32_t( getpagesize() );
26 assert( size >= pageSize );
27 assert( __builtin_popcount( size ) == 1 );
28 m_mapSize = size + pageSize;
29 auto mapAddr = mmap( nullptr, m_mapSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0 );
30 if( mapAddr == MAP_FAILED )
31 {
32 TracyDebug( "mmap failed: errno %i (%s)\n", errno, strerror( errno ) );
33 m_fd = 0;
34 m_metadata = nullptr;
35 close( fd );
36 return;
37 }
38 m_metadata = (perf_event_mmap_page*)mapAddr;
39 assert( m_metadata->data_offset == pageSize );
40 m_buffer = ((char*)mapAddr) + pageSize;
41 m_tail = m_metadata->data_tail;
42 }
43
44 ~RingBuffer()
45 {
46 if( m_metadata ) munmap( m_metadata, m_mapSize );
47 if( m_fd ) close( m_fd );
48 }
49
50 RingBuffer( const RingBuffer& ) = delete;
51 RingBuffer& operator=( const RingBuffer& ) = delete;
52
53 RingBuffer( RingBuffer&& other )
54 {
55 memcpy( (char*)&other, (char*)this, sizeof( RingBuffer ) );
56 m_metadata = nullptr;
57 m_fd = 0;
58 }
59
60 RingBuffer& operator=( RingBuffer&& other )
61 {
62 memcpy( (char*)&other, (char*)this, sizeof( RingBuffer ) );
63 m_metadata = nullptr;
64 m_fd = 0;
65 return *this;
66 }
67
68 bool IsValid() const { return m_metadata != nullptr; }
69 int GetId() const { return m_id; }
70 int GetCpu() const { return m_cpu; }
71
72 void Enable()
73 {
74 ioctl( m_fd, PERF_EVENT_IOC_ENABLE, 0 );
75 }
76
77 void Read( void* dst, uint64_t offset, uint64_t cnt )
78 {
79 const auto size = m_size;
80 auto src = ( m_tail + offset ) % size;
81 if( src + cnt <= size )
82 {
83 memcpy( dst, m_buffer + src, cnt );
84 }
85 else
86 {
87 const auto s0 = size - src;
88 const auto buf = m_buffer;
89 memcpy( dst, buf + src, s0 );
90 memcpy( (char*)dst + s0, buf, cnt - s0 );
91 }
92 }
93
94 void Advance( uint64_t cnt )
95 {
96 m_tail += cnt;
97 StoreTail();
98 }
99
100 bool CheckTscCaps() const
101 {
102 return m_metadata->cap_user_time_zero;
103 }
104
105 int64_t ConvertTimeToTsc( int64_t timestamp ) const
106 {
107 if( !m_metadata->cap_user_time_zero ) return 0;
108 const auto time = timestamp - m_metadata->time_zero;
109 const auto quot = time / m_metadata->time_mult;
110 const auto rem = time % m_metadata->time_mult;
111 return ( quot << m_metadata->time_shift ) + ( rem << m_metadata->time_shift ) / m_metadata->time_mult;
112 }
113
114 uint64_t LoadHead() const
115 {
116 return std::atomic_load_explicit( (const volatile std::atomic<uint64_t>*)&m_metadata->data_head, std::memory_order_acquire );
117 }
118
119 uint64_t GetTail() const
120 {
121 return m_tail;
122 }
123
124private:
125 void StoreTail()
126 {
127 std::atomic_store_explicit( (volatile std::atomic<uint64_t>*)&m_metadata->data_tail, m_tail, std::memory_order_release );
128 }
129
130 unsigned int m_size;
131 uint64_t m_tail;
132 char* m_buffer;
133 int m_id;
134 int m_cpu;
135 perf_event_mmap_page* m_metadata;
136
137 size_t m_mapSize;
138 int m_fd;
139};
140
141}