Messages in this thread | | | Date | Tue, 8 Jul 2003 00:48:36 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: 2.5.74-mm1 |
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On Tue, 8 Jul 2003, Daniel Phillips wrote:
> 1. 400ms buffers are hated by users, as was noted previously. They are > passable for some applications, but way too laggy for others. > > 2. Even if you are will to have a 400-500 ms buffer, if you can prove that you > will always meet that deadline, then it's a realtime system. > > 3. If you can show logically that you will nearly always meet the deadline, > it's a soft realtime system. That's what we're after here. From a design > standpoint, there are elegant soft realtime systems, and there are sucky > ones. > > 4. So how do you propose to "program timings" so that it's really hard to miss > those deadlines?
Having a backup of 400-500ms gives you an average hang-over of 200-250ms that are hardly noticeable by a human in this topic. The issue is not if you always meet the deadline, the issue is what amount of load will make you miss it. If I have to hire five ppl clicking and dragging on my desktop to make my player to skip, and it skips, I don't care if it missed the deadline. This because my desktop will hardly see that load. But if you have a 50-100ms backup, things turns out to be a little bit different. If you pretend to run a `make -jUNREAL` and still have the audio not skipping it is simply wrong. Running a `make -j20` in my machine shows an average of 24 TASK_RUNNING tasks, that even if they're granted with a mere 40ms timeslice, it'll take a full second before an expired task will see the light again. BTW, under such load RealPlayer skips badly, but I don't really care since it never did while I was doing all the normal (and many extra) stuff I'm doing on my desktop.
- Davide
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