Re: [PATCH] mm: yield during swap prefetching

Zan Lynx
2006-03-08T21:08:07Z

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On Wed, 2006-03-08 at 14:05 +1100, Con Kolivas wrote:
> André Goddard Rosa writes:
>
> > [...]
> >> > > Because being a serious desktop operating system that we are
> >> > > (bwahahahaha) means the user should not have special privileges to run
> >> > > something as simple as a game. Games should not need special scheduling
> >> > > classes. We can always use 'nice' for a compile though. Real time audio
> >> > > is a completely different world to this.
> > [...]
> >> Well as I said in my previous reply, games should _not_ need special
> >> scheduling classes. They are not written in a real time smart way and they do
> >> not have any realtime constraints or requirements.
> >
> > Sorry Con, but I have to disagree with you on this.
> >
> > Games are very complex software, involving heavy use of hardware resources
> > and they also have a lot of time constraints. So, I think they should
> > use RT priorities
> > if it is necessary to get the resources needed in time.
>
> Excellent, I've opened the can of worms.
>
> Yes, games are a in incredibly complex beast.
>
> No they shouldn't need real time scheduling to work well if they are coded
> properly. However, witness the fact that most of our games are windows
> ports, therefore being lower quality than the original. Witness also the
> fact that at last with dual core support, lots and lots (but not all) of
> windows games on _windows_ are having scheduling trouble and jerky playback,
> forcing them to crappily force binding to one cpu.
[snip]

Games where you notice frame-rate chop because the *disk system* is
using too much CPU are perfect examples of applications that should be
using real-time.

Multiple CPU cores and multithreading in games is another perfect
example of programming that *needs* predictable real-time thread
priorities. There is no other way to guarantee that physics processing
takes priority over graphics updates or AI, once each task becomes
separated from a monolithic main loop and spread over several CPU cores.

Because games often *are* badly written, a user-friendly Linux gaming
system does need a high-priority real-time task watching for a special
keystroke, like C-A-Del for example, so that it can kill the other
real-time tasks and return to the UI shell.

Games and real-time go together like they were made for each other.
--
Zan Lynx <zlynx@acm.org>

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