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pressure.go
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pressure.go
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// Package memsys provides memory management and slab/SGL allocation with io.Reader and io.Writer interfaces
// on top of scatter-gather lists of reusable buffers.
/*
* Copyright (c) 2018-2023, NVIDIA CORPORATION. All rights reserved.
*/
package memsys
import (
"fmt"
"github.com/NVIDIA/aistore/sys"
)
// memory _pressure_
const (
PressureLow = iota
PressureModerate
PressureHigh
PressureExtreme
OOM
)
const highLowThreshold = 40
var memPressureText = map[int]string{
PressureLow: "low",
PressureModerate: "moderate",
PressureHigh: "high",
PressureExtreme: "extreme",
OOM: "OOM",
}
// NOTE: used instead of mem.Free as a more realistic estimate where
// mem.BuffCache - kernel buffers and page caches that can be reclaimed -
// is always included _unless_ the resulting number exceeds mem.ActualFree
// (which is unlikely)
func memFree(mem *sys.MemStat) (free uint64) {
if free = mem.Free + mem.BuffCache; free > mem.ActualFree {
free = mem.ActualFree
}
return
}
// update swapping state
func (r *MMSA) updSwap(mem *sys.MemStat) {
var ncrit int32
swapping, crit := mem.SwapUsed > r.swap.size.Load(), r.swap.crit.Load()
if swapping {
ncrit = min(swappingMax, crit+1)
} else {
ncrit = max(0, crit-1)
}
r.swap.crit.Store(ncrit)
r.swap.size.Store(mem.SwapUsed)
}
// returns an estimate for the current memory pressure expressed as enumerated values
// also, tracks swapping stateful vars
func (r *MMSA) Pressure(mems ...*sys.MemStat) (pressure int) {
var mem *sys.MemStat
if len(mems) > 0 {
mem = mems[0]
} else {
mem = &sys.MemStat{}
_ = mem.Get()
}
free := memFree(mem)
ncrit := r.swap.crit.Load()
switch {
case ncrit > 2:
return OOM
case ncrit > 1 || mem.ActualFree <= r.MinFree:
return PressureExtreme
case ncrit > 0:
return PressureHigh
case free <= r.MinFree:
return PressureHigh
case free > r.lowWM+(r.lowWM>>4):
return PressureLow
}
pressure = PressureModerate
x := (free - r.MinFree) * 100 / (r.lowWM - r.MinFree)
if x < highLowThreshold {
pressure = PressureHigh
}
return
}
func (r *MMSA) pressure2S(p int) (sp string) {
sp = "pressure '" + memPressureText[p] + "'"
if crit := r.swap.crit.Load(); crit > 0 {
sp = fmt.Sprintf("%s, swapping(%d)", sp, crit)
}
return
}