Messages in this thread | | | Date | Sat, 26 Jan 2002 02:07:38 -0800 (PST) | From | Nigel Gamble <> | Subject | Re: [PATCH] syscall latency improvement #1 |
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On 25 Jan 2002, Robert Love wrote: > Mmm, I like it. Ingo Molnar talked to me about this (he wants such a > feature, too) earlier. This is a real win. > > This patch is beneficial to the kernel preemption patch.
Note that with a fully preemptible kernel, there is no need to test need_resched on return from system call, since any needed reschedule should already have been done. If the need_resched was set by an interrupt handler, the preempt_schedule on return from interrupt (or on exit from non-preemptible region) will have done the reschedule. And if need_resched was set because one process woke up another (higher priority) process, we can do the schedule() immediately, unless we are in a non-preemptible region in which case it will happen on exit from that region. I don't think we do an immediate schedule on wakeup yet but, with the existing preemption patch, that would make the test on syscall exit completely redundant (which may enable the cli instruction to be safely removed).
Nigel Gamble nigel@nrg.org Mountain View, CA, USA. http://www.nrg.org/
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