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runtime,cmd/trace: trace GC STW events

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Right now we only kind of sort of trace GC STW events. We emit events
around mark termination, but those start well after stopping the world
and end before starting it again, and we don't emit any events for
sweep termination.

Fix this by generalizing EvGCScanStart/EvGCScanDone. These were
already re-purposed to indicate mark termination (despite the names).
This commit renames them to EvGCSTWStart/EvGCSTWDone, adds an argument
to indicate the STW reason, and shuffles the runtime to generate them
right before stopping the world and right after starting the world,
respectively.

These events will make it possible to generate precise minimum mutator
utilization (MMU) graphs and could be useful in detecting
non-preemptible goroutines (e.g., #20792).

Change-Id: If95783f370781d8ef66addd94886028103a7c26f
Reviewed-on: https://go-review.googlesource.com/55411
Reviewed-by: Rick Hudson <rlh@golang.org>
This commit is contained in:
Austin Clements 2017-07-21 14:25:28 -04:00
parent 4a5c37793c
commit b0392159f6
8 changed files with 71 additions and 48 deletions
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61
src/internal/trace/parser.go
View file

@ -31,7 +31,7 @@ type Event struct {
SArgs []string // event-type-specific string args
// linked event (can be nil), depends on event type:
// for GCStart: the GCStop
// for GCScanStart: the GCScanDone
// for GCSTWStart: the GCSTWDone
// for GCSweepStart: the GCSweepDone
// for GoCreate: first GoStart of the created goroutine
// for GoStart/GoStartLabel: the associated GoEnd, GoBlock or other blocking event
@ -128,7 +128,7 @@ func readTrace(r io.Reader) (ver int, events []rawEvent, strings map[uint64]stri
return
}
switch ver {
case 1005, 1007, 1008, 1009:
case 1005, 1007, 1008, 1009, 1010:
// Note: When adding a new version, add canned traces
// from the old version to the test suite using mkcanned.bash.
break
@ -373,7 +373,18 @@ func parseEvents(ver int, rawEvents []rawEvent, strings map[uint64]string) (even
if raw.typ == EvGoStartLabel {
e.SArgs = []string{strings[e.Args[2]]}
}
case EvGCStart, EvGCDone, EvGCScanStart, EvGCScanDone:
case EvGCSTWStart:
e.G = 0
switch e.Args[0] {
case 0:
e.SArgs = []string{"mark termination"}
case 1:
e.SArgs = []string{"sweep termination"}
default:
err = fmt.Errorf("unknown STW kind %d", e.Args[0])
return
}
case EvGCStart, EvGCDone, EvGCSTWDone:
e.G = 0
case EvGoEnd, EvGoStop, EvGoSched, EvGoPreempt,
EvGoSleep, EvGoBlock, EvGoBlockSend, EvGoBlockRecv,
@ -511,14 +522,14 @@ func postProcessTrace(ver int, events []*Event) error {
type pdesc struct {
running bool
g uint64
evScan *Event
evSTW *Event
evSweep *Event
}
gs := make(map[uint64]gdesc)
ps := make(map[int]pdesc)
gs[0] = gdesc{state: gRunning}
var evGC *Event
var evGC, evSTW *Event
checkRunning := func(p pdesc, g gdesc, ev *Event, allowG0 bool) error {
name := EventDescriptions[ev.Type].Name
@ -565,17 +576,27 @@ func postProcessTrace(ver int, events []*Event) error {
}
evGC.Link = ev
evGC = nil
case EvGCScanStart:
if p.evScan != nil {
return fmt.Errorf("previous scanning is not ended before a new one (offset %v, time %v)", ev.Off, ev.Ts)
case EvGCSTWStart:
evp := &evSTW
if ver < 1010 {
// Before 1.10, EvGCSTWStart was per-P.
evp = &p.evSTW
}
p.evScan = ev
case EvGCScanDone:
if p.evScan == nil {
return fmt.Errorf("bogus scanning end (offset %v, time %v)", ev.Off, ev.Ts)
if *evp != nil {
return fmt.Errorf("previous STW is not ended before a new one (offset %v, time %v)", ev.Off, ev.Ts)
}
p.evScan.Link = ev
p.evScan = nil
*evp = ev
case EvGCSTWDone:
evp := &evSTW
if ver < 1010 {
// Before 1.10, EvGCSTWDone was per-P.
evp = &p.evSTW
}
if *evp == nil {
return fmt.Errorf("bogus STW end (offset %v, time %v)", ev.Off, ev.Ts)
}
(*evp).Link = ev
*evp = nil
case EvGCSweepStart:
if p.evSweep != nil {
return fmt.Errorf("previous sweeping is not ended before a new one (offset %v, time %v)", ev.Off, ev.Ts)
@ -864,6 +885,10 @@ func argNum(raw rawEvent, ver int) int {
if ver < 1007 {
narg-- // 1.7 added an additional seq arg
}
case EvGCSTWStart:
if ver < 1010 {
narg-- // 1.10 added an argument
}
}
return narg
}
@ -883,8 +908,8 @@ const (
EvProcStop = 6 // stop of P [timestamp]
EvGCStart = 7 // GC start [timestamp, seq, stack id]
EvGCDone = 8 // GC done [timestamp]
EvGCScanStart = 9 // GC mark termination start [timestamp]
EvGCScanDone = 10 // GC mark termination done [timestamp]
EvGCSTWStart = 9 // GC mark termination start [timestamp, kind]
EvGCSTWDone = 10 // GC mark termination done [timestamp]
EvGCSweepStart = 11 // GC sweep start [timestamp, stack id]
EvGCSweepDone = 12 // GC sweep done [timestamp, swept, reclaimed]
EvGoCreate = 13 // goroutine creation [timestamp, new goroutine id, new stack id, stack id]
@ -937,8 +962,8 @@ var EventDescriptions = [EvCount]struct {
EvProcStop: {"ProcStop", 1005, false, []string{}},
EvGCStart: {"GCStart", 1005, true, []string{"seq"}}, // in 1.5 format it was {}
EvGCDone: {"GCDone", 1005, false, []string{}},
EvGCScanStart: {"GCScanStart", 1005, false, []string{}},
EvGCScanDone: {"GCScanDone", 1005, false, []string{}},
EvGCSTWStart: {"GCSTWStart", 1005, false, []string{"kind"}}, // <= 1.9, args was {} (implicitly {0})
EvGCSTWDone: {"GCSTWDone", 1005, false, []string{}},
EvGCSweepStart: {"GCSweepStart", 1005, true, []string{}},
EvGCSweepDone: {"GCSweepDone", 1005, false, []string{"swept", "reclaimed"}}, // before 1.9, format was {}
EvGoCreate: {"GoCreate", 1005, true, []string{"g", "stack"}},