github.com/sitano/gsysint@v0.0.0-20190607084937-69a4f3233e4e/trace/trace.go

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Go execution tracer.
// The tracer captures a wide range of execution events like goroutine
// creation/blocking/unblocking, syscall enter/exit/block, GC-related events,
// changes of heap size, processor start/stop, etc and writes them to a buffer
// in a compact form. A precise nanosecond-precision timestamp and a stack
// trace is captured for most events.
// See https://golang.org/s/go15trace for more info.

package trace

import (
	"github.com/sitano/gsysint/sys"
)

// Event types in the trace, args are given in square brackets.
const (
	TraceEvNone              = 0  // unused
	TraceEvBatch             = 1  // start of per-P batch of events [pid, timestamp]
	TraceEvFrequency         = 2  // contains tracer timer frequency [frequency (ticks per second)]
	TraceEvStack             = 3  // stack [stack id, number of PCs, array of {PC, func string ID, file string ID, line}]
	TraceEvGomaxprocs        = 4  // current value of GOMAXPROCS [timestamp, GOMAXPROCS, stack id]
	TraceEvProcStart         = 5  // start of P [timestamp, thread id]
	TraceEvProcStop          = 6  // stop of P [timestamp]
	TraceEvGCStart           = 7  // GC start [timestamp, seq, stack id]
	TraceEvGCDone            = 8  // GC done [timestamp]
	TraceEvGCSTWStart        = 9  // GC STW start [timestamp, kind]
	TraceEvGCSTWDone         = 10 // GC STW done [timestamp]
	TraceEvGCSweepStart      = 11 // GC sweep start [timestamp, stack id]
	TraceEvGCSweepDone       = 12 // GC sweep done [timestamp, swept, reclaimed]
	TraceEvGoCreate          = 13 // goroutine creation [timestamp, new goroutine id, new stack id, stack id]
	TraceEvGoStart           = 14 // goroutine starts running [timestamp, goroutine id, seq]
	TraceEvGoEnd             = 15 // goroutine ends [timestamp]
	TraceEvGoStop            = 16 // goroutine stops (like in select{}) [timestamp, stack]
	TraceEvGoSched           = 17 // goroutine calls Gosched [timestamp, stack]
	TraceEvGoPreempt         = 18 // goroutine is preempted [timestamp, stack]
	TraceEvGoSleep           = 19 // goroutine calls Sleep [timestamp, stack]
	TraceEvGoBlock           = 20 // goroutine blocks [timestamp, stack]
	TraceEvGoUnblock         = 21 // goroutine is unblocked [timestamp, goroutine id, seq, stack]
	TraceEvGoBlockSend       = 22 // goroutine blocks on chan send [timestamp, stack]
	TraceEvGoBlockRecv       = 23 // goroutine blocks on chan recv [timestamp, stack]
	TraceEvGoBlockSelect     = 24 // goroutine blocks on select [timestamp, stack]
	TraceEvGoBlockSync       = 25 // goroutine blocks on Mutex/RWMutex [timestamp, stack]
	TraceEvGoBlockCond       = 26 // goroutine blocks on Cond [timestamp, stack]
	TraceEvGoBlockNet        = 27 // goroutine blocks on network [timestamp, stack]
	TraceEvGoSysCall         = 28 // syscall enter [timestamp, stack]
	TraceEvGoSysExit         = 29 // syscall exit [timestamp, goroutine id, seq, real timestamp]
	TraceEvGoSysBlock        = 30 // syscall blocks [timestamp]
	TraceEvGoWaiting         = 31 // denotes that goroutine is blocked when tracing starts [timestamp, goroutine id]
	TraceEvGoInSyscall       = 32 // denotes that goroutine is in syscall when tracing starts [timestamp, goroutine id]
	TraceEvHeapAlloc         = 33 // memstats.heap_live change [timestamp, heap_alloc]
	TraceEvNextGC            = 34 // memstats.next_gc change [timestamp, next_gc]
	TraceEvTimerGoroutine    = 35 // denotes timer goroutine [timer goroutine id]
	TraceEvFutileWakeup      = 36 // denotes that the previous wakeup of this goroutine was futile [timestamp]
	TraceEvString            = 37 // string dictionary entry [ID, length, string]
	TraceEvGoStartLocal      = 38 // goroutine starts running on the same P as the last event [timestamp, goroutine id]
	TraceEvGoUnblockLocal    = 39 // goroutine is unblocked on the same P as the last event [timestamp, goroutine id, stack]
	TraceEvGoSysExitLocal    = 40 // syscall exit on the same P as the last event [timestamp, goroutine id, real timestamp]
	TraceEvGoStartLabel      = 41 // goroutine starts running with label [timestamp, goroutine id, seq, label string id]
	TraceEvGoBlockGC         = 42 // goroutine blocks on GC assist [timestamp, stack]
	TraceEvGCMarkAssistStart = 43 // GC mark assist start [timestamp, stack]
	TraceEvGCMarkAssistDone  = 44 // GC mark assist done [timestamp]
	TraceEvUserTaskCreate    = 45 // trace.NewContext [timestamp, internal task id, internal parent task id, stack, name string]
	TraceEvUserTaskEnd       = 46 // end of a task [timestamp, internal task id, stack]
	TraceEvUserRegion        = 47 // trace.WithRegion [timestamp, internal task id, mode(0:start, 1:end), stack, name string]
	TraceEvUserLog           = 48 // trace.Log [timestamp, internal task id, key string id, stack, value string]
	TraceEvCount             = 49
	// Byte is used but only 6 bits are available for event type.
	// The remaining 2 bits are used to specify the number of arguments.
	// That means, the max event type value is 63.
)

const (
	// Timestamps in trace are cputicks/traceTickDiv.
	// This makes absolute values of timestamp diffs smaller,
	// and so they are encoded in less number of bytes.
	// 64 on x86 is somewhat arbitrary (one tick is ~20ns on a 3GHz machine).
	// The suggested increment frequency for PowerPC's time base register is
	// 512 MHz according to Power ISA v2.07 section 6.2, so we use 16 on ppc64
	// and ppc64le.
	// Tracing won't work reliably for architectures where cputicks is emulated
	// by nanotime, so the value doesn't matter for those architectures.
	TraceTickDiv = 16 + 48*(sys.Goarch386|sys.GoarchAmd64|sys.GoarchAmd64p32)
	// Maximum number of PCs in a single stack trace.
	// Since events contain only stack id rather than whole stack trace,
	// we can allow quite large values here.
	TraceStackSize = 128
	// Identifier of a fake P that is used when we trace without a real P.
	TraceGlobProc = -1
	// Maximum number of bytes to encode uint64 in base-128.
	TraceBytesPerNumber = 10
	// Shift of the number of arguments in the first event byte.
	TraceArgCountShift = 6
	// Flag passed to traceGoPark to denote that the previous wakeup of this
	// goroutine was futile. For example, a goroutine was unblocked on a mutex,
	// but another goroutine got ahead and acquired the mutex before the first
	// goroutine is scheduled, so the first goroutine has to block again.
	// Such wakeups happen on buffered channels and sync.Mutex,
	// but are generally not interesting for end user.
	TraceFutileWakeup byte = 128
)