expvar: improve Map.addKey for large number of keys
The existing implementation has poor performance for inserting large
number of keys because it chooses to append the new key to the sorted
keys array and then sort the new array again (time complexity is
O(nlogn)).
The improvement tries to utilize the sorted keys array by searching the
index and doing an insertion if any (time complexity is O(logn)).
Benchmarked on 4-core machine with `go test -cpu 1,2,4,8 -count 5
-benchmem -bench=.`(the equal results are omitted):
name old time/op new time/op delta
MapAddDifferentRandom-8 408µs ±11% 69µs ± 3% -82.95% (p=0.008 n=5+5)
MapAddDifferentRandom-4 389µs ±19% 69µs ± 2% -82.28% (p=0.008 n=5+5)
MapAddDifferentRandom-2 365µs ± 4% 75µs ± 6% -79.51% (p=0.008 n=5+5)
MapSetDifferentRandom-8 365µs ± 4% 76µs ±40% -79.07% (p=0.008 n=5+5)
MapAddDifferentRandom 366µs ± 3% 78µs ± 6% -78.66% (p=0.008 n=5+5)
MapSetDifferentRandom 369µs ± 2% 81µs ±34% -77.99% (p=0.008 n=5+5)
MapSetDifferentRandom-2 378µs ±10% 100µs ±32% -73.47% (p=0.008 n=5+5)
MapSetDifferentRandom-4 352µs ± 4% 108µs ± 7% -69.40% (p=0.008 n=5+5)
IntAdd-2 23.1ns ±21% 15.5ns ±23% -32.79% (p=0.032 n=5+5)
IntSet-2 21.4ns ±14% 16.7ns ±17% -22.00% (p=0.016 n=5+5)
FloatAdd-8 88.8ns ± 9% 70.8ns ±25% -20.23% (p=0.024 n=5+5)
FloatSet-2 22.3ns ±15% 17.8ns ±14% -20.14% (p=0.008 n=5+5)
IntAdd-8 21.7ns ± 3% 18.7ns ± 4% -14.00% (p=0.008 n=5+5)
MapAddDifferent-8 1.58µs ± 7% 1.42µs ± 6% -10.06% (p=0.016 n=5+5)
StringSet-2 42.4ns ± 1% 43.7ns ± 5% +3.07% (p=0.048 n=4+5)
FloatSet 8.27ns ± 2% 8.60ns ± 1% +3.94% (p=0.008 n=5+5)
FloatAdd 12.5ns ± 2% 13.0ns ± 4% +4.33% (p=0.032 n=5+5)
MapSetString-4 94.6ns ± 0% 101.7ns ± 4% +7.55% (p=0.016 n=4+5)
MapAddSameSteadyState-2 34.9ns ± 3% 37.7ns ± 5% +8.14% (p=0.008 n=5+5)
StringSet-4 34.5ns ± 0% 37.6ns ± 9% +9.02% (p=0.016 n=4+5)
MapSetDifferent-8 377ns ± 3% 411ns ± 7% +9.07% (p=0.008 n=5+5)
MapAddSameSteadyState 39.1ns ± 2% 42.8ns ± 6% +9.36% (p=0.008 n=5+5)
MapAddDifferentSteadyState 172ns ± 4% 190ns ± 9% +10.96% (p=0.016 n=5+5)
MapSet 143ns ± 4% 159ns ± 2% +11.06% (p=0.008 n=5+5)
MapSet-4 96.9ns ± 5% 107.8ns ± 6% +11.25% (p=0.008 n=5+5)
MapSet-2 102ns ± 6% 114ns ± 8% +11.94% (p=0.008 n=5+5)
IntSet 8.18ns ± 1% 12.78ns ±13% +56.31% (p=0.008 n=5+5)
name old alloc/op new alloc/op delta
MapSetDifferentRandom-4 19.8kB ± 0% 16.6kB ± 0% -16.21% (p=0.008 n=5+5)
MapSetDifferentRandom 19.8kB ± 0% 16.6kB ± 0% -16.21% (p=0.008 n=5+5)
MapSetDifferentRandom-8 19.8kB ± 0% 16.6kB ± 0% -16.20% (p=0.008 n=5+5)
MapSetDifferentRandom-2 19.8kB ± 0% 16.6kB ± 0% -16.20% (p=0.008 n=5+5)
MapAddDifferentRandom 20.6kB ± 0% 17.4kB ± 0% -15.57% (p=0.008 n=5+5)
MapAddDifferentRandom-8 20.6kB ± 0% 17.4kB ± 0% -15.57% (p=0.008 n=5+5)
MapAddDifferentRandom-2 20.6kB ± 0% 17.4kB ± 0% -15.56% (p=0.008 n=5+5)
MapAddDifferentRandom-4 20.6kB ± 0% 17.4kB ± 0% -15.56% (p=0.008 n=5+5)
MapAddDifferent 1.09kB ± 0% 0.96kB ± 0% -11.76% (p=0.008 n=5+5)
MapAddDifferent-2 1.09kB ± 0% 0.96kB ± 0% -11.76% (p=0.008 n=5+5)
MapAddDifferent-4 1.09kB ± 0% 0.96kB ± 0% -11.76% (p=0.008 n=5+5)
MapAddDifferent-8 1.09kB ± 0% 0.96kB ± 0% -11.76% (p=0.008 n=5+5)
MapAddSame 480B ± 0% 448B ± 0% -6.67% (p=0.008 n=5+5)
MapAddSame-2 480B ± 0% 448B ± 0% -6.67% (p=0.008 n=5+5)
MapAddSame-4 480B ± 0% 448B ± 0% -6.67% (p=0.008 n=5+5)
MapAddSame-8 480B ± 0% 448B ± 0% -6.67% (p=0.008 n=5+5)
name old allocs/op new allocs/op delta
MapSetDifferentRandom 423 ± 0% 323 ± 0% -23.64% (p=0.008 n=5+5)
MapSetDifferentRandom-2 423 ± 0% 323 ± 0% -23.64% (p=0.008 n=5+5)
MapSetDifferentRandom-4 423 ± 0% 323 ± 0% -23.64% (p=0.008 n=5+5)
MapSetDifferentRandom-8 423 ± 0% 323 ± 0% -23.64% (p=0.008 n=5+5)
MapAddDifferentRandom 523 ± 0% 423 ± 0% -19.12% (p=0.008 n=5+5)
MapAddDifferentRandom-2 523 ± 0% 423 ± 0% -19.12% (p=0.008 n=5+5)
MapAddDifferentRandom-4 523 ± 0% 423 ± 0% -19.12% (p=0.008 n=5+5)
MapAddDifferentRandom-8 523 ± 0% 423 ± 0% -19.12% (p=0.008 n=5+5)
MapAddDifferent 31.0 ± 0% 27.0 ± 0% -12.90% (p=0.008 n=5+5)
MapAddDifferent-2 31.0 ± 0% 27.0 ± 0% -12.90% (p=0.008 n=5+5)
MapAddDifferent-4 31.0 ± 0% 27.0 ± 0% -12.90% (p=0.008 n=5+5)
MapAddDifferent-8 31.0 ± 0% 27.0 ± 0% -12.90% (p=0.008 n=5+5)
MapAddSame 11.0 ± 0% 10.0 ± 0% -9.09% (p=0.008 n=5+5)
MapAddSame-2 11.0 ± 0% 10.0 ± 0% -9.09% (p=0.008 n=5+5)
MapAddSame-4 11.0 ± 0% 10.0 ± 0% -9.09% (p=0.008 n=5+5)
MapAddSame-8 11.0 ± 0% 10.0 ± 0% -9.09% (p=0.008 n=5+5)
Fixes #31414
Change-Id: I2dd655dec9dbbf8d7881a0f3f8edcb3d29199a48
GitHub-Last-Rev:
a816fe3f62498481500a0ce9695de9fd3aa9f7b7
GitHub-Pull-Request: golang/go#31418
Reviewed-on: https://go-review.googlesource.com/c/go/+/171718
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>