Messages in this thread | | | Date | Fri, 12 Sep 2003 22:56:55 -0400 | From | Iker <> | Subject | Re: [lkml] RE: self piping and context switching |
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More specifically, I was wondering if the write to the pipe or the call back into poll involved anything that might prompt the scheduler to replace the thread in this scenario.
> It's reasonable to expect that this will be the most common case and the > one to optimize. It is unreasonable to fail if this doesn't happen, since > it's not guaranteed to happen. Note that if by "without a context switch" > you really mean without another thread getting a chance to run, then it is > totally unreasonable.
Are you referring to transitions to/from kernel space? If so, wouldn't the write on the pipe and the call to poll both result in transitions?
Regards, Iker
----- Original Message ----- From: "David Schwartz" <davids@webmaster.com> To: "Iker" <iker@computer.org>; <linux-kernel@vger.kernel.org> Sent: Friday, September 12, 2003 10:04 PM Subject: [lkml] RE: self piping and context switching
> > > Assume a thread is monitoring a set of fd's which include both ends of > > a pipe (using poll, for example). If the thread writes to the pipe (in > > order to notify itself for whatever reason) is it reasonable to expect > > that it will be able to return to its poll loop and get the event > > without a context switch? (provided it quickly returns to the poll > > loop). > > It's reasonable to expect that this will be the most common case and the > one to optimize. It is unreasonable to fail if this doesn't happen, since > it's not guaranteed to happen. Note that if by "without a context switch" > you really mean without another thread getting a chance to run, then it is > totally unreasonable. On SMP systems and with hyper-threading, threads can > run concurrently. > > DS > > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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