Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 13 Apr 2006 14:18:45 -0700 | From | "Nish Aravamudan" <> | Subject | Re: select takes too much time |
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On 4/13/06, linux-os (Dick Johnson) <linux-os@analogic.com> wrote: > > On Thu, 13 Apr 2006, Ram Gupta wrote: > > > On 4/13/06, Michal Schmidt <xschmi00@stud.feec.vutbr.cz> wrote: > >> Ram Gupta wrote: > >>> I am using 2.5.45 kernel but I believe the same would be the true > >>> for the latest kernel too. > >> > >> Are you just assuming this, or did you actually try a recent kernel? > >> > >> Michal > >> > > > > I didn't get a chance to try it on a recent kernel yet but I believe > > it to be so though I may be wrong > > > > Ram > > - > > Simple program here shows that you may be right! In principle, > I should be able to multiply the loop-count by 10 and divide > the sleep time by 10, still resulting in 1-second total time > through the loop. Not so! Changing the value, marked "Change this" to > a smaller value doesn't affect the time very much. It is as though > the sleep time is always at least 1000 microseconds. If this is > correct, then there should be some kind of warning that the time > can't be less than the HZ value, or whatever is limiting it.
Doesn't sys_select() just use schedule_timeout() eventually? <checks> yes, sys_select() -> core_sys_select() -> do_select() -> schedule_timeout(). Presuming there is any value stored in the timeout parameter, you're going to sleep at least a jiffy which is 1/HZ. If HZ=1000 (or 1024), I'd guess that 1000 us as a minimum would be expected.
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