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UNIcodeX/workq.nim

Created November 12, 2020 14:49
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  1. UNIcodeX revised this gist Nov 12, 2020. No changes.
  2. UNIcodeX created this gist Nov 12, 2020.
    99 changes: 99 additions & 0 deletions workq.nim
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    # nim c -r --threads:on --gc:orc

    import cpuinfo, os, random, locks, deques

    type
    WorkReq = ref object
    id: int

    WorkRes = ref object
    id: int
    data: seq[int]

    var
    workThreads: array[32, Thread[int]]
    inputQ: Deque[WorkReq]
    inputLock: Lock
    outputQ: Deque[WorkRes]
    outputLock: Lock

    template hold(lock: Lock, body: untyped) =
    ## Wraps withLock in a gcsafe block.
    {.gcsafe.}:
    withLock lock:
    body

    proc workThread(threadNum: int) {.thread.} =
    ## Work thread waits for work to arrive then does it.
    ## N of them can be running at one time.
    while true:
    var
    ready = false
    workReq: WorkReq
    hold inputLock:
    ready = inputQ.len > 0
    if ready:
    workReq = inputQ.popFirst()
    if ready:
    var workRes = WorkRes()
    workRes.id = workReq.id
    workRes.data = newSeq[int](500)
    var z = workRes.id

    # Do the actual work.
    for n in 0 .. 10_000:
    for i in 0 ..< workRes.data.len:
    z = z mod 10 + z div 10
    workRes.data[i] = z

    hold outputLock:
    outputQ.addLast(workRes)

    proc askForWork() =
    ## Asks for work to be done.
    while true:
    sleep(0)

    var inputLen, outputLen: int
    # Its best to never hold 2 locks at the same time.
    hold inputLock:
    inputLen = inputQ.len
    hold outputLock:
    outputLen = outputQ.len
    # echo "inputLen: ", inputLen, " outputLen: ", outputLen

    # Keep the work q at 10 works always.
    for i in 0 ..< 10 - inputLen:
    var workReq = WorkReq()
    workReq.id = rand(0 .. 10_000)
    # echo "need ", workReq.id
    hold inputLock:
    inputQ.addLast(workReq)

    # Get works back if any.
    while true:
    var
    ready = false
    workRes: WorkRes
    hold outputLock:
    ready = outputQ.len > 0
    if ready:
    workRes = outputQ.popFirst()
    if ready:
    echo "got ", workRes.id
    else:
    break

    # Init the two locks.
    inputLock.initLock()
    outputLock.initLock()

    # Start number of works threads as we have CPUs.
    # Leave 1 cpu for the main thread.
    # Leave 1 cpu for all other programs.
    for i in 0 ..< clamp(countProcessors() - 2, 1, 32):
    createThread(workThreads[i], workThread, i)
    # Don't pin to 0th core as thats where most of the IO happens.
    pinToCpu(workThreads[i], i + 1)

    askForWork()