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runtime: convert timeHistogram to atomic types
I've dropped the note that sched.timeToRun is protected by sched.lock, as it does not seem to be true. For #53821. Change-Id: I03f8dc6ca0bcd4ccf3ec113010a0aa39c6f7d6ef Reviewed-on: https://go-review.googlesource.com/c/go/+/419449 Reviewed-by: Austin Clements <austin@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Run-TryBot: Michael Pratt <mpratt@google.com>
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@ -17,8 +17,6 @@ var AtomicFields = []uintptr{
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unsafe.Offsetof(p{}.timer0When),
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unsafe.Offsetof(p{}.timerModifiedEarliest),
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unsafe.Offsetof(p{}.gcFractionalMarkTime),
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unsafe.Offsetof(schedt{}.timeToRun),
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unsafe.Offsetof(timeHistogram{}.underflow),
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unsafe.Offsetof(profBuf{}.overflow),
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unsafe.Offsetof(profBuf{}.overflowTime),
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unsafe.Offsetof(heapStatsDelta{}.tinyAllocCount),
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@ -37,10 +35,8 @@ var AtomicFields = []uintptr{
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unsafe.Offsetof(lfnode{}.next),
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unsafe.Offsetof(mstats{}.last_gc_nanotime),
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unsafe.Offsetof(mstats{}.last_gc_unix),
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unsafe.Offsetof(mstats{}.gcPauseDist),
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unsafe.Offsetof(ticksType{}.val),
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unsafe.Offsetof(workType{}.bytesMarked),
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unsafe.Offsetof(timeHistogram{}.counts),
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}
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// AtomicVariables is the set of global variables on which we perform
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@ -1244,9 +1244,9 @@ func (th *TimeHistogram) Count(bucket, subBucket uint) (uint64, bool) {
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t := (*timeHistogram)(th)
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i := bucket*TimeHistNumSubBuckets + subBucket
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if i >= uint(len(t.counts)) {
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return t.underflow, false
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return t.underflow.Load(), false
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}
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return t.counts[i], true
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return t.counts[i].Load(), true
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}
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func (th *TimeHistogram) Record(duration int64) {
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@ -66,18 +66,16 @@ const (
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// It is an HDR histogram with exponentially-distributed
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// buckets and linearly distributed sub-buckets.
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//
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// Counts in the histogram are updated atomically, so it is safe
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// for concurrent use. It is also safe to read all the values
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// atomically.
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// The histogram is safe for concurrent reads and writes.
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type timeHistogram struct {
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counts [timeHistNumSuperBuckets * timeHistNumSubBuckets]uint64
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counts [timeHistNumSuperBuckets * timeHistNumSubBuckets]atomic.Uint64
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// underflow counts all the times we got a negative duration
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// sample. Because of how time works on some platforms, it's
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// possible to measure negative durations. We could ignore them,
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// but we record them anyway because it's better to have some
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// signal that it's happening than just missing samples.
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underflow uint64
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underflow atomic.Uint64
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}
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// record adds the given duration to the distribution.
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@ -88,7 +86,7 @@ type timeHistogram struct {
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//go:nosplit
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func (h *timeHistogram) record(duration int64) {
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if duration < 0 {
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atomic.Xadd64(&h.underflow, 1)
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h.underflow.Add(1)
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return
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}
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// The index of the exponential bucket is just the index
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@ -116,7 +114,7 @@ func (h *timeHistogram) record(duration int64) {
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} else {
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subBucket = uint(duration)
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}
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atomic.Xadd64(&h.counts[superBucket*timeHistNumSubBuckets+subBucket], 1)
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h.counts[superBucket*timeHistNumSubBuckets+subBucket].Add(1)
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}
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const (
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@ -7,7 +7,6 @@ package runtime
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// Metrics implementation exported to runtime/metrics.
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import (
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"runtime/internal/atomic"
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"unsafe"
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)
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@ -197,9 +196,9 @@ func initMetrics() {
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// The bottom-most bucket, containing negative values, is tracked
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// as a separately as underflow, so fill that in manually and then
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// iterate over the rest.
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hist.counts[0] = atomic.Load64(&memstats.gcPauseDist.underflow)
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hist.counts[0] = memstats.gcPauseDist.underflow.Load()
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for i := range memstats.gcPauseDist.counts {
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hist.counts[i+1] = atomic.Load64(&memstats.gcPauseDist.counts[i])
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hist.counts[i+1] = memstats.gcPauseDist.counts[i].Load()
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}
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},
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},
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@ -327,9 +326,9 @@ func initMetrics() {
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"/sched/latencies:seconds": {
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compute: func(_ *statAggregate, out *metricValue) {
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hist := out.float64HistOrInit(timeHistBuckets)
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hist.counts[0] = atomic.Load64(&sched.timeToRun.underflow)
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hist.counts[0] = sched.timeToRun.underflow.Load()
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for i := range sched.timeToRun.counts {
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hist.counts[i+1] = atomic.Load64(&sched.timeToRun.counts[i])
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hist.counts[i+1] = sched.timeToRun.counts[i].Load()
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}
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},
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},
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@ -334,10 +334,6 @@ func init() {
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println(offset)
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throw("memstats.heapStats not aligned to 8 bytes")
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}
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if offset := unsafe.Offsetof(memstats.gcPauseDist); offset%8 != 0 {
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println(offset)
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throw("memstats.gcPauseDist not aligned to 8 bytes")
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}
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// Ensure the size of heapStatsDelta causes adjacent fields/slots (e.g.
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// [3]heapStatsDelta) to be 8-byte aligned.
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if size := unsafe.Sizeof(heapStatsDelta{}); size%8 != 0 {
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@ -703,11 +703,6 @@ func schedinit() {
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sigsave(&gp.m.sigmask)
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initSigmask = gp.m.sigmask
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if offset := unsafe.Offsetof(sched.timeToRun); offset%8 != 0 {
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println(offset)
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throw("sched.timeToRun not aligned to 8 bytes")
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}
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goargs()
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goenvs()
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parsedebugvars()
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@ -843,8 +843,6 @@ type schedt struct {
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// timeToRun is a distribution of scheduling latencies, defined
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// as the sum of time a G spends in the _Grunnable state before
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// it transitions to _Grunning.
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//
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// timeToRun is protected by sched.lock.
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timeToRun timeHistogram
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}
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