runtime, time: remove old timer code
Updates #6239
Updates #27707
Change-Id: I65e6471829c9de4677d3ac78ef6cd7aa0a1fc4cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/171884
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index c648195..d264e1d 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -4410,44 +4410,23 @@
}
// Maybe jump time forward for playground.
- if oldTimers {
- gp := timejumpOld()
- if gp != nil {
- casgstatus(gp, _Gwaiting, _Grunnable)
- globrunqput(gp)
- _p_ := pidleget()
- if _p_ == nil {
- throw("checkdead: no p for timer")
+ _p_ := timejump()
+ if _p_ != nil {
+ for pp := &sched.pidle; *pp != 0; pp = &(*pp).ptr().link {
+ if (*pp).ptr() == _p_ {
+ *pp = _p_.link
+ break
}
- mp := mget()
- if mp == nil {
- // There should always be a free M since
- // nothing is running.
- throw("checkdead: no m for timer")
- }
- mp.nextp.set(_p_)
- notewakeup(&mp.park)
- return
}
- } else {
- _p_ := timejump()
- if _p_ != nil {
- for pp := &sched.pidle; *pp != 0; pp = &(*pp).ptr().link {
- if (*pp).ptr() == _p_ {
- *pp = _p_.link
- break
- }
- }
- mp := mget()
- if mp == nil {
- // There should always be a free M since
- // nothing is running.
- throw("checkdead: no m for timer")
- }
- mp.nextp.set(_p_)
- notewakeup(&mp.park)
- return
+ mp := mget()
+ if mp == nil {
+ // There should always be a free M since
+ // nothing is running.
+ throw("checkdead: no m for timer")
}
+ mp.nextp.set(_p_)
+ notewakeup(&mp.park)
+ return
}
// There are no goroutines running, so we can look at the P's.
diff --git a/src/runtime/time.go b/src/runtime/time.go
index ed044b3..a7d14cf 100644
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -7,24 +7,17 @@
package runtime
import (
- "internal/cpu"
"runtime/internal/atomic"
"runtime/internal/sys"
"unsafe"
)
-// Temporary scaffolding while the new timer code is added.
-const oldTimers = false
-
// Package time knows the layout of this structure.
// If this struct changes, adjust ../time/sleep.go:/runtimeTimer.
type timer struct {
- tb *timersBucket // the bucket the timer lives in (oldTimers)
- i int // heap index (oldTimers)
-
// If this timer is on a heap, which P's heap it is on.
// puintptr rather than *p to match uintptr in the versions
- // of this struct defined in other packages. (!oldTimers)
+ // of this struct defined in other packages.
pp puintptr
// Timer wakes up at when, and then at when+period, ... (period > 0 only)
@@ -36,55 +29,13 @@
arg interface{}
seq uintptr
- // What to set the when field to in timerModifiedXX status. (!oldTimers)
+ // What to set the when field to in timerModifiedXX status.
nextwhen int64
- // The status field holds one of the values below. (!oldTimers)
+ // The status field holds one of the values below.
status uint32
}
-// timersLen is the length of timers array.
-//
-// Ideally, this would be set to GOMAXPROCS, but that would require
-// dynamic reallocation
-//
-// The current value is a compromise between memory usage and performance
-// that should cover the majority of GOMAXPROCS values used in the wild.
-const timersLen = 64
-
-// timers contains "per-P" timer heaps.
-//
-// Timers are queued into timersBucket associated with the current P,
-// so each P may work with its own timers independently of other P instances.
-//
-// Each timersBucket may be associated with multiple P
-// if GOMAXPROCS > timersLen.
-var timers [timersLen]struct {
- timersBucket
-
- // The padding should eliminate false sharing
- // between timersBucket values.
- pad [cpu.CacheLinePadSize - unsafe.Sizeof(timersBucket{})%cpu.CacheLinePadSize]byte
-}
-
-func (t *timer) assignBucket() *timersBucket {
- id := uint8(getg().m.p.ptr().id) % timersLen
- t.tb = &timers[id].timersBucket
- return t.tb
-}
-
-//go:notinheap
-type timersBucket struct {
- lock mutex
- gp *g
- created bool
- sleeping bool
- rescheduling bool
- sleepUntil int64
- waitnote note
- t []*timer
-}
-
// Code outside this file has to be careful in using a timer value.
//
// The pp, status, and nextwhen fields may only be used by code in this file.
@@ -226,11 +177,6 @@
// timeSleep puts the current goroutine to sleep for at least ns nanoseconds.
//go:linkname timeSleep time.Sleep
func timeSleep(ns int64) {
- if oldTimers {
- timeSleepOld(ns)
- return
- }
-
if ns <= 0 {
return
}
@@ -257,30 +203,6 @@
return true
}
-func timeSleepOld(ns int64) {
- if ns <= 0 {
- return
- }
-
- gp := getg()
- t := gp.timer
- if t == nil {
- t = new(timer)
- gp.timer = t
- }
- *t = timer{}
- t.when = nanotime() + ns
- t.f = goroutineReady
- t.arg = gp
- tb := t.assignBucket()
- lock(&tb.lock)
- if !tb.addtimerLocked(t) {
- unlock(&tb.lock)
- badTimer()
- }
- goparkunlock(&tb.lock, waitReasonSleep, traceEvGoSleep, 3)
-}
-
// startTimer adds t to the timer heap.
//go:linkname startTimer time.startTimer
func startTimer(t *timer) {
@@ -318,11 +240,6 @@
// That avoids the risk of changing the when field of a timer in some P's heap,
// which could cause the heap to become unsorted.
func addtimer(t *timer) {
- if oldTimers {
- addtimerOld(t)
- return
- }
-
// when must never be negative; otherwise runtimer will overflow
// during its delta calculation and never expire other runtime timers.
if t.when < 0 {
@@ -370,59 +287,11 @@
return siftupTimer(pp.timers, i)
}
-func addtimerOld(t *timer) {
- tb := t.assignBucket()
- lock(&tb.lock)
- ok := tb.addtimerLocked(t)
- unlock(&tb.lock)
- if !ok {
- badTimer()
- }
-}
-
-// Add a timer to the heap and start or kick timerproc if the new timer is
-// earlier than any of the others.
-// Timers are locked.
-// Returns whether all is well: false if the data structure is corrupt
-// due to user-level races.
-func (tb *timersBucket) addtimerLocked(t *timer) bool {
- // when must never be negative; otherwise timerproc will overflow
- // during its delta calculation and never expire other runtime timers.
- if t.when < 0 {
- t.when = 1<<63 - 1
- }
- t.i = len(tb.t)
- tb.t = append(tb.t, t)
- if !siftupTimer(tb.t, t.i) {
- return false
- }
- if t.i == 0 {
- // siftup moved to top: new earliest deadline.
- if tb.sleeping && tb.sleepUntil > t.when {
- tb.sleeping = false
- notewakeup(&tb.waitnote)
- }
- if tb.rescheduling {
- tb.rescheduling = false
- goready(tb.gp, 0)
- }
- if !tb.created {
- tb.created = true
- go timerproc(tb)
- }
- }
- return true
-}
-
// deltimer deletes the timer t. It may be on some other P, so we can't
// actually remove it from the timers heap. We can only mark it as deleted.
// It will be removed in due course by the P whose heap it is on.
// Reports whether the timer was removed before it was run.
func deltimer(t *timer) bool {
- if oldTimers {
- return deltimerOld(t)
- }
-
for {
switch s := atomic.Load(&t.status); s {
case timerWaiting, timerModifiedLater:
@@ -513,62 +382,9 @@
return ok
}
-func deltimerOld(t *timer) bool {
- if t.tb == nil {
- // t.tb can be nil if the user created a timer
- // directly, without invoking startTimer e.g
- // time.Ticker{C: c}
- // In this case, return early without any deletion.
- // See Issue 21874.
- return false
- }
-
- tb := t.tb
-
- lock(&tb.lock)
- removed, ok := tb.deltimerLocked(t)
- unlock(&tb.lock)
- if !ok {
- badTimer()
- }
- return removed
-}
-
-func (tb *timersBucket) deltimerLocked(t *timer) (removed, ok bool) {
- // t may not be registered anymore and may have
- // a bogus i (typically 0, if generated by Go).
- // Verify it before proceeding.
- i := t.i
- last := len(tb.t) - 1
- if i < 0 || i > last || tb.t[i] != t {
- return false, true
- }
- if i != last {
- tb.t[i] = tb.t[last]
- tb.t[i].i = i
- }
- tb.t[last] = nil
- tb.t = tb.t[:last]
- ok = true
- if i != last {
- if !siftupTimer(tb.t, i) {
- ok = false
- }
- if !siftdownTimer(tb.t, i) {
- ok = false
- }
- }
- return true, ok
-}
-
// modtimer modifies an existing timer.
// This is called by the netpoll code.
func modtimer(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
- if oldTimers {
- modtimerOld(t, when, period, f, arg, seq)
- return
- }
-
if when < 0 {
when = maxWhen
}
@@ -652,35 +468,11 @@
}
}
-func modtimerOld(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
- tb := t.tb
-
- lock(&tb.lock)
- _, ok := tb.deltimerLocked(t)
- if ok {
- t.when = when
- t.period = period
- t.f = f
- t.arg = arg
- t.seq = seq
- ok = tb.addtimerLocked(t)
- }
- unlock(&tb.lock)
- if !ok {
- badTimer()
- }
-}
-
// resettimer resets an existing inactive timer to turn it into an active timer,
// with a new time for when the timer should fire.
// This should be called instead of addtimer if the timer value has been,
// or may have been, used previously.
func resettimer(t *timer, when int64) {
- if oldTimers {
- resettimerOld(t, when)
- return
- }
-
if when < 0 {
when = maxWhen
}
@@ -727,82 +519,6 @@
}
}
-func resettimerOld(t *timer, when int64) {
- t.when = when
- addtimer(t)
-}
-
-// Timerproc runs the time-driven events.
-// It sleeps until the next event in the tb heap.
-// If addtimer inserts a new earlier event, it wakes timerproc early.
-func timerproc(tb *timersBucket) {
- tb.gp = getg()
- for {
- lock(&tb.lock)
- tb.sleeping = false
- now := nanotime()
- delta := int64(-1)
- for {
- if len(tb.t) == 0 {
- delta = -1
- break
- }
- t := tb.t[0]
- delta = t.when - now
- if delta > 0 {
- break
- }
- ok := true
- if t.period > 0 {
- // leave in heap but adjust next time to fire
- t.when += t.period * (1 + -delta/t.period)
- if !siftdownTimer(tb.t, 0) {
- ok = false
- }
- } else {
- // remove from heap
- last := len(tb.t) - 1
- if last > 0 {
- tb.t[0] = tb.t[last]
- tb.t[0].i = 0
- }
- tb.t[last] = nil
- tb.t = tb.t[:last]
- if last > 0 {
- if !siftdownTimer(tb.t, 0) {
- ok = false
- }
- }
- t.i = -1 // mark as removed
- }
- f := t.f
- arg := t.arg
- seq := t.seq
- unlock(&tb.lock)
- if !ok {
- badTimer()
- }
- if raceenabled {
- raceacquire(unsafe.Pointer(t))
- }
- f(arg, seq)
- lock(&tb.lock)
- }
- if delta < 0 || faketime > 0 {
- // No timers left - put goroutine to sleep.
- tb.rescheduling = true
- goparkunlock(&tb.lock, waitReasonTimerGoroutineIdle, traceEvGoBlock, 1)
- continue
- }
- // At least one timer pending. Sleep until then.
- tb.sleeping = true
- tb.sleepUntil = now + delta
- noteclear(&tb.waitnote)
- unlock(&tb.lock)
- notetsleepg(&tb.waitnote, delta)
- }
-}
-
// cleantimers cleans up the head of the timer queue. This speeds up
// programs that create and delete timers; leaving them in the heap
// slows down addtimer. Reports whether no timer problems were found.
@@ -1199,55 +915,9 @@
return minP
}
-func timejumpOld() *g {
- if faketime == 0 {
- return nil
- }
-
- for i := range timers {
- lock(&timers[i].lock)
- }
- gp := timejumpLocked()
- for i := range timers {
- unlock(&timers[i].lock)
- }
-
- return gp
-}
-
-func timejumpLocked() *g {
- // Determine a timer bucket with minimum when.
- var minT *timer
- for i := range timers {
- tb := &timers[i]
- if !tb.created || len(tb.t) == 0 {
- continue
- }
- t := tb.t[0]
- if minT == nil || t.when < minT.when {
- minT = t
- }
- }
- if minT == nil || minT.when <= faketime {
- return nil
- }
-
- faketime = minT.when
- tb := minT.tb
- if !tb.rescheduling {
- return nil
- }
- tb.rescheduling = false
- return tb.gp
-}
-
// timeSleepUntil returns the time when the next timer should fire.
// This is only called by sysmon.
func timeSleepUntil() int64 {
- if oldTimers {
- return timeSleepUntilOld()
- }
-
next := int64(maxWhen)
// Prevent allp slice changes. This is like retake.
@@ -1298,27 +968,6 @@
return next
}
-func timeSleepUntilOld() int64 {
- next := int64(1<<63 - 1)
-
- // Determine minimum sleepUntil across all the timer buckets.
- //
- // The function can not return a precise answer,
- // as another timer may pop in as soon as timers have been unlocked.
- // So lock the timers one by one instead of all at once.
- for i := range timers {
- tb := &timers[i]
-
- lock(&tb.lock)
- if tb.sleeping && tb.sleepUntil < next {
- next = tb.sleepUntil
- }
- unlock(&tb.lock)
- }
-
- return next
-}
-
// Heap maintenance algorithms.
// These algorithms check for slice index errors manually.
// Slice index error can happen if the program is using racy
@@ -1326,9 +975,6 @@
// it will cause the program to crash with a mysterious
// "panic holding locks" message. Instead, we panic while not
// holding a lock.
-// The races can occur despite the bucket locks because assignBucket
-// itself is called without locks, so racy calls can cause a timer to
-// change buckets while executing these functions.
func siftupTimer(t []*timer, i int) bool {
if i >= len(t) {
@@ -1342,12 +988,10 @@
break
}
t[i] = t[p]
- t[i].i = i
i = p
}
if tmp != t[i] {
t[i] = tmp
- t[i].i = i
}
return true
}
@@ -1385,12 +1029,10 @@
break
}
t[i] = t[c]
- t[i].i = i
i = c
}
if tmp != t[i] {
t[i] = tmp
- t[i].i = i
}
return true
}
diff --git a/src/runtime/trace.go b/src/runtime/trace.go
index 65d9a38..9aa9fac 100644
--- a/src/runtime/trace.go
+++ b/src/runtime/trace.go
@@ -54,7 +54,7 @@
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]
+ traceEvTimerGoroutine = 35 // not currently used; previously denoted 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]
@@ -416,13 +416,6 @@
var data []byte
data = append(data, traceEvFrequency|0<<traceArgCountShift)
data = traceAppend(data, uint64(freq))
- for i := range timers {
- tb := &timers[i]
- if tb.gp != nil {
- data = append(data, traceEvTimerGoroutine|0<<traceArgCountShift)
- data = traceAppend(data, uint64(tb.gp.goid))
- }
- }
// This will emit a bunch of full buffers, we will pick them up
// on the next iteration.
trace.stackTab.dump()
diff --git a/src/time/sleep.go b/src/time/sleep.go
index adce860..4e61d0a 100644
--- a/src/time/sleep.go
+++ b/src/time/sleep.go
@@ -11,10 +11,7 @@
// Interface to timers implemented in package runtime.
// Must be in sync with ../runtime/time.go:/^type timer
type runtimeTimer struct {
- tb uintptr
- i int
- pp uintptr
-
+ pp uintptr
when int64
period int64
f func(interface{}, uintptr) // NOTE: must not be closure
