NumGC int64 // number of garbage collections
PauseTotal time.Duration // total pause for all collections
Pause []time.Duration // pause history, most recent first
+ PauseEnd []time.Time // pause end times history, most recent first
PauseQuantiles []time.Duration
}
func ReadGCStats(stats *GCStats) {
// Create a buffer with space for at least two copies of the
// pause history tracked by the runtime. One will be returned
- // to the caller and the other will be used as a temporary buffer
- // for computing quantiles.
+ // to the caller and the other will be used as transfer buffer
+ // for end times history and as a temporary buffer for
+ // computing quantiles.
const maxPause = len(((*runtime.MemStats)(nil)).PauseNs)
- if cap(stats.Pause) < 2*maxPause {
- stats.Pause = make([]time.Duration, 2*maxPause)
+ if cap(stats.Pause) < 2*maxPause+3 {
+ stats.Pause = make([]time.Duration, 2*maxPause+3)
}
- // readGCStats fills in the pause history (up to maxPause entries)
- // and then three more: Unix ns time of last GC, number of GC,
- // and total pause time in nanoseconds. Here we depend on the
- // fact that time.Duration's native unit is nanoseconds, so the
- // pauses and the total pause time do not need any conversion.
+ // readGCStats fills in the pause and end times histories (up to
+ // maxPause entries) and then three more: Unix ns time of last GC,
+ // number of GC, and total pause time in nanoseconds. Here we
+ // depend on the fact that time.Duration's native unit is
+ // nanoseconds, so the pauses and the total pause time do not need
+ // any conversion.
readGCStats(&stats.Pause)
n := len(stats.Pause) - 3
stats.LastGC = time.Unix(0, int64(stats.Pause[n]))
stats.NumGC = int64(stats.Pause[n+1])
stats.PauseTotal = stats.Pause[n+2]
+ n /= 2 // buffer holds pauses and end times
stats.Pause = stats.Pause[:n]
+ if cap(stats.PauseEnd) < maxPause {
+ stats.PauseEnd = make([]time.Time, 0, maxPause)
+ }
+ stats.PauseEnd = stats.PauseEnd[:0]
+ for _, ns := range stats.Pause[n : n+n] {
+ stats.PauseEnd = append(stats.PauseEnd, time.Unix(0, int64(ns)))
+ }
+
if len(stats.PauseQuantiles) > 0 {
if n == 0 {
for i := range stats.PauseQuantiles {
t.Errorf("stats.PauseQuantiles[%d]=%d > stats.PauseQuantiles[%d]=%d", i, q[i], i+1, q[i+1])
}
}
+
+ // compare memory stats with gc stats:
+ if len(stats.PauseEnd) != n {
+ t.Fatalf("len(stats.PauseEnd) = %d, want %d", len(stats.PauseEnd), n)
+ }
+ off := (int(mstats.NumGC) + len(mstats.PauseEnd) - 1) % len(mstats.PauseEnd)
+ for i := 0; i < n; i++ {
+ dt := stats.PauseEnd[i]
+ if dt.UnixNano() != int64(mstats.PauseEnd[off]) {
+ t.Errorf("stats.PauseEnd[%d] = %d, want %d", i, dt, mstats.PauseEnd[off])
+ }
+ off = (off + len(mstats.PauseEnd) - 1) % len(mstats.PauseEnd)
+ }
}
var big = make([]byte, 1<<20)
uint64 next_gc; // next GC (in heap_alloc time)
uint64 last_gc; // last GC (in absolute time)
uint64 pause_total_ns;
- uint64 pause_ns[256];
+ uint64 pause_ns[256]; // circular buffer of recent GC pause lengths
+ uint64 pause_end[256]; // circular buffer of recent GC end times (nanoseconds since 1970)
uint32 numgc;
bool enablegc;
bool debuggc;
NextGC uint64 // next collection will happen when HeapAlloc ≥ this amount
LastGC uint64 // end time of last collection (nanoseconds since 1970)
PauseTotalNs uint64
- PauseNs [256]uint64 // circular buffer of recent GC pause times, most recent at [(NumGC+255)%256]
+ PauseNs [256]uint64 // circular buffer of recent GC pause durations, most recent at [(NumGC+255)%256]
+ PauseEnd [256]uint64 // circular buffer of recent GC pause end times
NumGC uint32
EnableGC bool
DebugGC bool
t4 = runtime·nanotime();
runtime·atomicstore64(&mstats.last_gc, runtime·unixnanotime()); // must be Unix time to make sense to user
mstats.pause_ns[mstats.numgc%nelem(mstats.pause_ns)] = t4 - t0;
+ mstats.pause_end[mstats.numgc%nelem(mstats.pause_end)] = t4;
mstats.pause_total_ns += t4 - t0;
mstats.numgc++;
if(mstats.debuggc)
{
Slice *pauses;
uint64 *p;
- uint32 i, n;
+ uint32 i, j, n;
pauses = g->m->ptrarg[0];
g->m->ptrarg[0] = nil;
if(pauses->cap < nelem(mstats.pause_ns)+3)
runtime·throw("runtime: short slice passed to readGCStats");
- // Pass back: pauses, last gc (absolute time), number of gc, total pause ns.
+ // Pass back: pauses, pause ends, last gc (absolute time), number of gc, total pause ns.
p = (uint64*)pauses->array;
runtime·lock(&runtime·mheap.lock);
+
n = mstats.numgc;
if(n > nelem(mstats.pause_ns))
n = nelem(mstats.pause_ns);
-
+
// The pause buffer is circular. The most recent pause is at
// pause_ns[(numgc-1)%nelem(pause_ns)], and then backward
// from there to go back farther in time. We deliver the times
// most recent first (in p[0]).
- for(i=0; i<n; i++)
- p[i] = mstats.pause_ns[(mstats.numgc-1-i)%nelem(mstats.pause_ns)];
+ for(i=0; i<n; i++) {
+ j = (mstats.numgc-1-i)%nelem(mstats.pause_ns);
+ p[i] = mstats.pause_ns[j];
+ p[n+i] = mstats.pause_end[j];
+ }
- p[n] = mstats.last_gc;
- p[n+1] = mstats.numgc;
- p[n+2] = mstats.pause_total_ns;
+ p[n+n] = mstats.last_gc;
+ p[n+n+1] = mstats.numgc;
+ p[n+n+2] = mstats.pause_total_ns;
runtime·unlock(&runtime·mheap.lock);
- pauses->len = n+3;
+ pauses->len = n+n+3;
}
void