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tailscale/tstest/allocs.go

52 lines
1.4 KiB
Go

// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tstest
import (
"fmt"
"runtime"
"testing"
"time"
)
// MinAllocsPerRun asserts that f can run with no more than target allocations.
// It runs f up to 1000 times or 5s, whichever happens first.
// If f has executed more than target allocations on every run, it returns a non-nil error.
//
// MinAllocsPerRun sets GOMAXPROCS to 1 during its measurement and restores
// it before returning.
func MinAllocsPerRun(t *testing.T, target uint64, f func()) error {
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
var memstats runtime.MemStats
var min, max, sum uint64
start := time.Now()
var iters int
for {
runtime.ReadMemStats(&memstats)
startMallocs := memstats.Mallocs
f()
runtime.ReadMemStats(&memstats)
mallocs := memstats.Mallocs - startMallocs
// TODO: if mallocs < target, return an error? See discussion in #3204.
if mallocs <= target {
return nil
}
if min == 0 || mallocs < min {
min = mallocs
}
if mallocs > max {
max = mallocs
}
sum += mallocs
iters++
if iters == 1000 || time.Since(start) > 5*time.Second {
break
}
}
return fmt.Errorf("min allocs = %d, max allocs = %d, avg allocs/run = %f, want run with <= %d allocs", min, max, float64(sum)/float64(iters), target)
}