expvar: reduce sync.Map overhead for (*Map).Set (e9702c0c) · Commits · go / golang

Commit e9702c0c authored Apr 30, 2017 by

Bryan C. Mills Committed by Bryan Mills May 02, 2017

expvar: reduce sync.Map overhead for (*Map).Set

Use Load instead of LoadOrStore in the fast path to save 1 alloc/op
for existing keys.

name old time/op new time/op delta
IntAdd 6.39ns ± 7% 6.97ns ±19% ~ (p=0.105 n=8+8)
IntAdd-6 12.3ns ± 1% 12.2ns ± 1% ~ (p=0.396 n=7+7)
IntSet 6.41ns ± 6% 6.94ns ±21% ~ (p=0.168 n=8+8)
IntSet-6 12.1ns ± 3% 11.7ns ± 9% ~ (p=0.496 n=7+8)
FloatAdd 14.3ns ± 9% 14.7ns ± 4% ~ (p=0.088 n=8+8)
FloatAdd-6 36.5ns ± 1% 36.6ns ± 0% ~ (p=0.709 n=7+6)
FloatSet 6.59ns ± 7% 6.47ns ± 7% ~ (p=0.397 n=8+7)
FloatSet-6 12.2ns ± 1% 12.2ns ± 2% ~ (p=0.748 n=7+7)
StringSet 67.8ns ± 6% 68.7ns ± 6% ~ (p=0.342 n=8+8)
StringSet-6 41.8ns ± 5% 41.7ns ± 5% ~ (p=0.979 n=8+8)
MapSet 294ns ± 6% 234ns ± 4% -20.35% (p=0.000 n=8+8)
MapSet-6 95.8ns ± 2% 89.4ns ± 3% -6.73% (p=0.000 n=8+8)
MapSetDifferent 1.31µs ± 5% 1.07µs ± 4% -18.21% (p=0.000 n=8+8)
MapSetDifferent-6 260ns ± 8% 210ns ± 9% -19.44% (p=0.000 n=8+8)
MapSetString 294ns ± 6% 236ns ± 4% -19.92% (p=0.000 n=8+8)
MapSetString-6 95.6ns ± 2% 89.9ns ± 2% -5.97% (p=0.000 n=7+8)
MapAddSame 1.46µs ± 3% 1.46µs ± 5% ~ (p=0.721 n=8+8)
MapAddSame-6 328ns ± 6% 330ns ± 4% ~ (p=0.776 n=8+8)
MapAddDifferent 4.89µs ± 7% 4.98µs ± 6% ~ (p=0.505 n=8+8)
MapAddDifferent-6 1.02µs ± 3% 1.01µs ± 4% ~ (p=0.352 n=7+8)
MapAddSameSteadyState 62.1ns ± 7% 60.8ns ± 4% ~ (p=0.521 n=8+8)
MapAddSameSteadyState-6 38.1ns ± 3% 37.7ns ± 0% ~ (p=0.185 n=7+6)
MapAddDifferentSteadyState 290ns ± 5% 293ns ± 4% ~ (p=0.515 n=8+8)
MapAddDifferentSteadyState-6 63.0ns ± 7% 63.7ns ±11% ~ (p=0.482 n=7+8)
RealworldExpvarUsage 7.39µs ± 5% 7.51µs ± 5% ~ (p=0.382 n=8+8)
RealworldExpvarUsage-6 3.07µs ±28% 3.04µs ±43% ~ (p=0.798 n=8+8)

name old alloc/op new alloc/op delta
IntAdd 0.00B 0.00B ~ (all equal)
IntAdd-6 0.00B 0.00B ~ (all equal)
IntSet 0.00B 0.00B ~ (all equal)
IntSet-6 0.00B 0.00B ~ (all equal)
FloatAdd 0.00B 0.00B ~ (all equal)
FloatAdd-6 0.00B 0.00B ~ (all equal)
FloatSet 0.00B 0.00B ~ (all equal)
FloatSet-6 0.00B 0.00B ~ (all equal)
StringSet 16.0B ± 0% 16.0B ± 0% ~ (all equal)
StringSet-6 16.0B ± 0% 16.0B ± 0% ~ (all equal)
MapSet 48.0B ± 0% 32.0B ± 0% -33.33% (p=0.000 n=8+8)
MapSet-6 48.0B ± 0% 32.0B ± 0% -33.33% (p=0.000 n=8+8)
MapSetDifferent 192B ± 0% 128B ± 0% -33.33% (p=0.000 n=8+8)
MapSetDifferent-6 192B ± 0% 128B ± 0% -33.33% (p=0.000 n=8+8)
MapSetString 48.0B ± 0% 32.0B ± 0% -33.33% (p=0.000 n=8+8)
MapSetString-6 48.0B ± 0% 32.0B ± 0% -33.33% (p=0.000 n=8+8)
MapAddSame 480B ± 0% 480B ± 0% ~ (all equal)
MapAddSame-6 480B ± 0% 480B ± 0% ~ (all equal)
MapAddDifferent 1.09kB ± 0% 1.09kB ± 0% ~ (all equal)
MapAddDifferent-6 1.09kB ± 0% 1.09kB ± 0% ~ (all equal)
MapAddSameSteadyState 0.00B 0.00B ~ (all equal)
MapAddSameSteadyState-6 0.00B 0.00B ~ (all equal)
MapAddDifferentSteadyState 0.00B 0.00B ~ (all equal)
MapAddDifferentSteadyState-6 0.00B 0.00B ~ (all equal)
RealworldExpvarUsage 0.00B 0.00B ~ (all equal)
RealworldExpvarUsage-6 0.00B 0.00B ~ (all equal)

name old allocs/op new allocs/op delta
IntAdd 0.00 0.00 ~ (all equal)
IntAdd-6 0.00 0.00 ~ (all equal)
IntSet 0.00 0.00 ~ (all equal)
IntSet-6 0.00 0.00 ~ (all equal)
FloatAdd 0.00 0.00 ~ (all equal)
FloatAdd-6 0.00 0.00 ~ (all equal)
FloatSet 0.00 0.00 ~ (all equal)
FloatSet-6 0.00 0.00 ~ (all equal)
StringSet 1.00 ± 0% 1.00 ± 0% ~ (all equal)
StringSet-6 1.00 ± 0% 1.00 ± 0% ~ (all equal)
MapSet 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.000 n=8+8)
MapSet-6 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.000 n=8+8)
MapSetDifferent 12.0 ± 0% 8.0 ± 0% -33.33% (p=0.000 n=8+8)
MapSetDifferent-6 12.0 ± 0% 8.0 ± 0% -33.33% (p=0.000 n=8+8)
MapSetString 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.000 n=8+8)
MapSetString-6 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.000 n=8+8)
MapAddSame 11.0 ± 0% 11.0 ± 0% ~ (all equal)
MapAddSame-6 11.0 ± 0% 11.0 ± 0% ~ (all equal)
MapAddDifferent 31.0 ± 0% 31.0 ± 0% ~ (all equal)
MapAddDifferent-6 31.0 ± 0% 31.0 ± 0% ~ (all equal)
MapAddSameSteadyState 0.00 0.00 ~ (all equal)
MapAddSameSteadyState-6 0.00 0.00 ~ (all equal)
MapAddDifferentSteadyState 0.00 0.00 ~ (all equal)
MapAddDifferentSteadyState-6 0.00 0.00 ~ (all equal)
RealworldExpvarUsage 0.00 0.00 ~ (all equal)
RealworldExpvarUsage-6 0.00 0.00 ~ (all equal)

https://perf.golang.org/search?q=upload:20170501.1

Change-Id: I28fc3906473f2b7307f6d1ae05a8d9b01ef8a6f8
Reviewed-on: https://go-review.googlesource.com/42211
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

parent 48def43f

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View file @ e9702c0c

@@ -142,11 +142,17 @@ func (v *Map) Get(key string) Var {
+}
 func (v *Map) Set(key string, av Var) {
 	if _, dup := v.m.LoadOrStore(key, av); dup {
 		v.m.Store(key, av)
 	} else {
 		v.addKey(key)
 	// Before we store the value, check to see whether the key is new. Try a Load
 	// before LoadOrStore: LoadOrStore causes the key interface to escape even on
 	// the Load path.
 	if _, ok := v.m.Load(key); !ok {
 		if _, dup := v.m.LoadOrStore(key, av); !dup {
 			v.addKey(key)
 			return
+		}
+	}
 	v.m.Store(key, av)
+}
 // Add adds delta to the *Int value stored under the given map key.
-...

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