1 /* 2 * Copyright (C) 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "perfetto/base/metatrace.h" 18 19 #include <fcntl.h> 20 #include <stdlib.h> 21 22 #include "perfetto/base/build_config.h" 23 #include "perfetto/base/file_utils.h" 24 #include "perfetto/base/time.h" 25 26 #if PERFETTO_BUILDFLAG(PERFETTO_OS_WIN) 27 #include <corecrt_io.h> 28 #endif 29 30 namespace perfetto { 31 namespace base { 32 33 namespace { 34 int MaybeOpenTraceFile() { 35 static const char* tracing_path = getenv("PERFETTO_METATRACE_FILE"); 36 if (tracing_path == nullptr) 37 return -1; 38 static int fd = open(tracing_path, O_WRONLY | O_CREAT | O_TRUNC, 0644); 39 return fd; 40 } 41 } // namespace 42 43 constexpr uint32_t MetaTrace::kMainThreadCpu; 44 45 void MetaTrace::WriteEvent(char type, const char* evt_name, size_t cpu) { 46 int fd = MaybeOpenTraceFile(); 47 if (fd == -1) 48 return; 49 50 // The JSON event format expects both "pid" and "tid" fields to create 51 // per-process tracks. Here what we really want to achieve is having one track 52 // per cpu. So we just pretend that each CPU is its own process with 53 // pid == tid == cpu. 54 char json[256]; 55 int len = sprintf(json, 56 "{\"ts\": %f, \"cat\": \"PERF\", \"ph\": \"%c\", \"name\": " 57 "\"%s\", \"pid\": %zu, \"tid\": %zu},\n", 58 GetWallTimeNs().count() / 1000.0, type, evt_name, cpu, cpu); 59 ignore_result(WriteAll(fd, json, static_cast<size_t>(len))); 60 } 61 62 } // namespace base 63 } // namespace perfetto 64
