On Tue, Aug 24, 2010 at 3:47 PM, Neil Toronto <neil.toro...@gmail.com> wrote: > Matthias Felleisen wrote: >> >> Catching up with some mail. >> Neil wrote: >>> >>> Avoiding allocation reduces GC collects, which reduces stutters and >>> hitches. >> >> My (possibly old) understanding of GC and mutation tell me that this >> is one of those prejudices that programmers should get rid of. Every >> mutation goes across an access barrier in a GC like ours and can thus >> be much more expensive than a lightweight allocation. This was >> certainly true for early generational collectors. I do know that the >> hordes of Java programmers who invaded GCLand forced GC builders to >> make C/C++-like programs in Java work reasonably fast with collectors >> and so collectors changed. > > In my defense, I was talking about framerate, not total or average cost of > memory management. A GC pause in my game test app lasts 50ms to 200ms, which > causes a "hitch": a noticeable, temporary drop in framerate and > responsiveness, in this case down to 20Hz to 5Hz. For comparison, 60Hz is an > ideal minimum. A sequence of minor hitches is a stutter; sometimes Racket's > GC pause causes those as well. > > Inflicting hitches on users in a twitch game is a cardinal sin. In > non-twitch games they are eye-wrenching, especially when everything else is > smooth. Games are really almost real-time apps.
Totally disagree. Here's a crazy forum where you will find people complaining about how a recent release (DeathSmiles - North America for Xbox360) is garbage because there isn't ENOUGH slowdown as compared to the Japanese 360 or XBox release: http://www.aksysgames.com/forums/topic/732 I do agree that you personally don't want a drop in frame rate and that the GC gets in your way of achieving that goal. Jay > > I'm still doing the game universe-style, so I haven't moved to mutation yet. > I'm halfheartedly considering it. I'll probably try an allocation pool of > same/similar-sized arrays first. I'd gladly pay half of my ideal 16ms per > frame to eliminate hitches. > > Neil T > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev > -- Jay McCarthy <j...@cs.byu.edu> Assistant Professor / Brigham Young University http://teammccarthy.org/jay "The glory of God is Intelligence" - D&C 93 _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
