[Stackless] Santa concurrency problem

[Richard Tew]

On 3/26/07, Carlos Eduardo de Paula <carlosedp at gmail.com> wrote:
> What is taking a hit on CPU is the ManageSleepingTasklets tasklet, it
> gets that usage in its loop.
>
> What I can do for throttling the cpu usage is put a time.sleep(0.001)
> inside the while loop, with it we can have a decent precision on time
> (1 milisecond) and having the CPU at low usage...
>
> Maybe Richard can help us out about a cleaner solution on this...

The Sleep code here is copied from the simple example I wrote.
Unfortunately like most low level Stackless examples it only
really serves to demonstrate what you can do, now how you should
do it in all cases.  In the case here, since it is responsible for
awakening tasklets and if it knows none are waking anytime
soon, it is safe to avoid a busy wait by adapting the code to
use time.sleep for the interim.

  def ManageSleepingTasklets(self):
    while True:
      if len(self.sleepingTasklets):
        endTime = self.sleepingTasklets[0][0]
        if endTime <= time.time():
          channel = self.sleepingTasklets[0][1]
          del self.sleepingTasklets[0]
          # We have to send something, but it doesn't matter what as
it is not used.
          channel.send(None)
        elif stackless.runcount == 1:
          # We are the only tasklet running, the rest are blocked on
channels sleeping.
          # We can call time.sleep until the first awakens to avoid a busy wait.
          delay = endTime - time.time()
          print "wait delay", delay
          time.sleep(delay)
      stackless.schedule()

Cheers,
Richard.

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