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// Copyright 2015-2021 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pse
// On macs after some studying it seems that typical tools like ps and activity monitor report MaxRss and not
// current RSS. I wrote some C code to pull the real RSS and although it does not go down very often, when it does
// that is not reflected in the typical tooling one might compare us to, so we can skip cgo and just use rusage imo.
// We also do not use virtual memory in the upper layers at all, so ok to skip since rusage does not report vss.
import (
"math"
"sync"
"syscall"
"time"
)
type lastUsage struct {
sync.Mutex
last time.Time
cpu time.Duration
rss int64
pcpu float64
}
// To hold the last usage and call time.
var lu lastUsage
func init() {
updateUsage()
periodic()
}
// Get our usage.
func getUsage() (now time.Time, cpu time.Duration, rss int64) {
var ru syscall.Rusage
syscall.Getrusage(syscall.RUSAGE_SELF, &ru)
now = time.Now()
cpu = time.Duration(ru.Utime.Sec)*time.Second + time.Duration(ru.Utime.Usec)*time.Microsecond
cpu += time.Duration(ru.Stime.Sec)*time.Second + time.Duration(ru.Stime.Usec)*time.Microsecond
return now, cpu, ru.Maxrss
}
// Update last usage.
// We need to have a prior sample to compute pcpu.
func updateUsage() (pcpu float64, rss int64) {
lu.Lock()
defer lu.Unlock()
now, cpu, rss := getUsage()
// Don't skew pcpu by sampling too close to last sample.
if elapsed := now.Sub(lu.last); elapsed < 500*time.Millisecond {
// Always update rss.
lu.rss = rss
} else {
tcpu := float64(cpu - lu.cpu)
lu.last, lu.cpu, lu.rss = now, cpu, rss
// Want to make this one decimal place and not count on upper layers.
// Cores already taken into account via cpu time measurements.
lu.pcpu = math.Round(tcpu/float64(elapsed)*1000) / 10
}
return lu.pcpu, lu.rss
}
// Sampling function to keep pcpu relevant.
func periodic() {
updateUsage()
time.AfterFunc(time.Second, periodic)
}
// ProcUsage returns CPU and memory usage.
// Note upper layers do not use virtual memory size, so ok that it is not filled in here.
func ProcUsage(pcpu *float64, rss, vss *int64) error {
*pcpu, *rss = updateUsage()
return nil
}
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