Messages in this thread | | | Date | Tue, 12 Aug 2003 17:07:13 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] O13int for interactivity |
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Mike Galbraith wrote:
> At 12:51 PM 8/12/2003 +1000, Nick Piggin wrote: > > >> Rob Landley wrote: >> >>> On Tuesday 05 August 2003 06:32, Nick Piggin wrote: >>> >>> >>>> But by employing the kernel's services in the shape of a blocking >>>> syscall, all sleeps are intentional. >>> >>> >>> Wrong. Some sleeps indicate "I have run out of stuff to do right >>> now, I'm going to wait for a timer or another process or something >>> to wake me up with new work". >>> >>> >>> >>> Some sleeps indicate "ideally this would run on an enormous ramdisk >>> attached to gigabit ethernet, but hard drives and internet >>> connections are just too slow so my true CPU-hogness is hidden by >>> the fact I'm running on a PC instead of a mainframe." >> >> >> I don't quite understand what you are getting at, but if you don't >> want to >> sleep you should be able to use a non blocking syscall. But in some >> cases >> I think there are times when you may not be able to use a non >> blocking call. >> And if a process is a CPU hog, its a CPU hog. If its not its not. >> Doesn't >> matter how it would behave on another system. > > > Ah, but there is something there. Take the X and xmms's gl thread > thingy I posted a while back. (X runs long enough to expire in the > presence of a couple of low priority cpu hogs. gl thread, which is a > mondo cpu hog, and normally runs and runs and runs at cpu hog > priority, suddenly acquires extreme interactive priority, and X, which > is normally sleepy suddenly becomes permanently runnable at cpu hog > priority) The gl thread starts sleeping because X isn't getting > enough cpu to be able to get it's work done and go to sleep. The gl > thread isn't voluntarily sleeping, and X isn't voluntarily running. > The behavior change is forced upon both.
It does... It is I tell ya!
Look, the gl thread is probably _very_ explicitly asking to sleep. No I don't know how X works, but I have an idea that select is generally used as an event notification, right?
Now the gl thread is essentially saying "wait until X finishes the work I've given it, or I get some other event": ie. "put me to sleep until this fd becomes readable".
OK maybe your scenario is a big problem. Its not due to any imagined semantics in the way things are sleeping. Its due to the scheduler.
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