1 /*
2 * Copyright (c) 2021 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15 #define HILOG_TAG "RingBuffer"
16
17 #include <linux/perf_event.h>
18 #include "ring_buffer.h"
19 #include "perf_event_record.h"
20 #if defined(is_ohos) && is_ohos
21 #include "hiperf_hilog.h"
22 #endif
23
24 namespace OHOS {
25 namespace Developtools {
26 namespace HiPerf {
RingBuffer(size_t size)27 RingBuffer::RingBuffer(size_t size) : size_(size)
28 {
29 if (size > 0) {
30 buf_ = std::make_unique<uint8_t[]>(size);
31 }
32 }
33
~RingBuffer()34 RingBuffer::~RingBuffer() {}
35
36 // get size of the writable space
GetFreeSize() const37 size_t RingBuffer::GetFreeSize() const
38 {
39 return size_ - (head_.load(std::memory_order_relaxed) - tail_.load(std::memory_order_relaxed));
40 }
41
AllocForWrite(size_t writeSize)42 uint8_t *RingBuffer::AllocForWrite(size_t writeSize)
43 {
44 if (buf_ == nullptr || buf_.get() == nullptr) {
45 return nullptr;
46 }
47 size_t writeHead = head_.load(std::memory_order_relaxed);
48 size_t readHead = tail_.load(std::memory_order_acquire);
49 if (size_ == 0) {
50 return nullptr;
51 }
52 size_t writePos = writeHead % size_;
53 size_t readPos = readHead % size_;
54 writeSize_ = writeSize;
55 if (writePos < readPos) {
56 // |---writePos<---writeSize--->readPos---|
57 if (writePos + writeSize > readPos) {
58 return nullptr;
59 }
60 } else if (writePos == readPos and writeHead != readHead) {
61 // writePos catch up with readPos, but buffer is full
62 return nullptr;
63 } else {
64 // two cases: 1, writePos catch up with readPos, but buffer is empty
65 // 2, |---readPos---writePos<---writeSize--->|
66 if (writePos + writeSize > size_) {
67 // no enough space at the end
68 if (readPos < writeSize) {
69 return nullptr;
70 }
71 // wrap to the start, set mark byte
72 buf_.get()[writePos] = MARGIN_BYTE;
73 writeSize_ += (size_ - writePos);
74 writePos = 0;
75 }
76 }
77
78 return buf_.get() + writePos;
79 }
80
EndWrite()81 void RingBuffer::EndWrite()
82 {
83 size_t head = head_.load(std::memory_order_relaxed);
84 head += writeSize_;
85 head_.store(head, std::memory_order_release);
86 }
87
GetReadData()88 uint8_t *RingBuffer::GetReadData()
89 {
90 CHECK_TRUE(buf_ == nullptr || buf_.get() == nullptr, nullptr, 0, "");
91 size_t writeHead = head_.load(std::memory_order_acquire);
92 size_t readHead = tail_.load(std::memory_order_relaxed);
93 if (writeHead == readHead) {
94 return nullptr;
95 }
96
97 readSize_ = 0;
98 if (size_ == 0) {
99 return nullptr;
100 }
101 size_t writePos = writeHead % size_;
102 size_t readPos = readHead % size_;
103 if (writePos <= readPos) {
104 // |<---data2--->writePos---readPos<---data1--->|
105 if (buf_.get()[readPos] == MARGIN_BYTE) {
106 CHECK_TRUE(writePos == 0, nullptr, 0, "");
107 readSize_ = (size_ - readPos);
108 readPos = 0;
109 }
110 }
111 // else |---readPos<---data--->writePos---|
112 perf_event_header *header = reinterpret_cast<perf_event_header *>(buf_.get() + readPos);
113 CHECK_TRUE(header == nullptr, nullptr, 0, "");
114
115 if (header->type == PERF_RECORD_AUXTRACE) {
116 struct PerfRecordAuxtraceData *auxtrace = reinterpret_cast<struct PerfRecordAuxtraceData *>(header + 1);
117 readSize_ += header->size + auxtrace->size;
118 } else {
119 readSize_ += header->size;
120 }
121 return buf_.get() + readPos;
122 }
123
EndRead()124 void RingBuffer::EndRead()
125 {
126 size_t tail = tail_.load(std::memory_order_relaxed);
127 tail += readSize_;
128 tail_.store(tail, std::memory_order_release);
129 }
130 } // namespace HiPerf
131 } // namespace Developtools
132 } // namespace OHOS
133