Messages in this thread | | | Date | Wed, 27 Jun 2001 23:22:19 +0200 | From | Manfred Spraul <> | Subject | Re: wake_up vs. wake_up_sync |
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> I'm having trouble understanding the difference between these. > Synchronous apparently causes try_to_wake_up() to NOT call > reschedule_idle() but I'm uncertain what reschedule_idle() is doing. I > assume it just looks for an idle CPU and makes that CPU reschedule. > > What is the purpose of wake_up_sync?
Avoid the reschedule_idle() call - it's quite costly, and it could cause processes jumping from one cpu to another.
> Why would you want to prevent > reschedule_idle()? > If one process runs, wakes up another process and _knows_ that it's going to sleep immediately after the wake_up it doesn't need the reschedule_idle: the current cpu will be idle soon, the scheduler doesn't need to find another cpu for the woken up thread.
I think the pipe code is the only user of _sync right now - pipes cause an incredible amount of task switches.
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