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#
#
# Nim's Runtime Library
# (c) Copyright 2015 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## This module implements a helper for a thread pool to determine whether
## creating a thread is a good idea.
when defined(windows):
import winlean, os, strutils, math
proc `-`(a, b: FILETIME): int64 = a.rdFileTime - b.rdFileTime
elif defined(linux):
from cpuinfo import countProcessors
type
ThreadPoolAdvice* = enum
doNothing,
doCreateThread, # create additional thread for throughput
doShutdownThread # too many threads are busy, shutdown one
ThreadPoolState* = object
when defined(windows):
prevSysKernel, prevSysUser, prevProcKernel, prevProcUser: FILETIME
calls*: int
proc advice*(s: var ThreadPoolState): ThreadPoolAdvice =
when defined(windows):
var
sysIdle, sysKernel, sysUser,
procCreation, procExit, procKernel, procUser: FILETIME
if getSystemTimes(sysIdle, sysKernel, sysUser) == 0 or
getProcessTimes(Handle(-1), procCreation, procExit,
procKernel, procUser) == 0:
return doNothing
if s.calls > 0:
let
sysKernelDiff = sysKernel - s.prevSysKernel
sysUserDiff = sysUser - s.prevSysUser
procKernelDiff = procKernel - s.prevProcKernel
procUserDiff = procUser - s.prevProcUser
sysTotal = int(sysKernelDiff + sysUserDiff)
procTotal = int(procKernelDiff + procUserDiff)
# total CPU usage < 85% --> create a new worker thread.
# Measurements show that 100% and often even 90% is not reached even
# if all my cores are busy.
if sysTotal == 0 or procTotal / sysTotal < 0.85:
result = doCreateThread
s.prevSysKernel = sysKernel
s.prevSysUser = sysUser
s.prevProcKernel = procKernel
s.prevProcUser = procUser
elif defined(linux):
proc fscanf(c: File, frmt: cstring) {.varargs, importc,
header: "<stdio.h>".}
var f = open("/proc/loadavg")
var b: float
var busy, total: int
fscanf(f,"%lf %lf %lf %ld/%ld",
addr b, addr b, addr b, addr busy, addr total)
f.close()
let cpus = countProcessors()
if busy-1 < cpus:
result = doCreateThread
elif busy-1 >= cpus*2:
result = doShutdownThread
else:
result = doNothing
else:
# XXX implement this for other OSes
result = doNothing
inc s.calls
when not defined(testing) and isMainModule:
proc busyLoop() =
while true:
discard random(80)
os.sleep(100)
spawn busyLoop()
spawn busyLoop()
spawn busyLoop()
spawn busyLoop()
var s: ThreadPoolState
for i in 1 .. 70:
echo advice(s)
os.sleep(1000)
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