4 ms·

Their lower end target is 10 ms. In a game, 16 ms is your entire time budget.

arianvanp 8y ago
In VR your budget is 11 ms and you can't miss it or the entire frame is thrown away and you introduce a frame of latency to compensate. So for VR these kind of effects of GC are even worse.
- chipperyman573 8y ago
  Also, while most games are fine with losing a frame or two every few minutes, in VR dropping frames will cause motion sickness really fast. FPS is, from what I've observed, the most important part of a VR game. If you're dropping frames or stuttering, the experience will suffer greatly When I was developing a VR game, my team noticed that some ultra-sensitive people started to get sick when we would drop around five frames (the vive displays 90, so this is only a ~5% drop). There was more to it (dropping a few frames every few minutes was usually fine, but consistently dropping frames every second or two is an issue).
spricket 8y ago
10 ms isn't all that much. When games load in assets they'll do various things like malloc huge chunks and you lose a few frames. If GC only causes occasional (maybe every 2 minutes) loss of a frame or two it should be no problem. If you watch benchmark FPS traces that count every frame delay you'll see that occasional stutters happen in basically every game. Loss of a single frame just isn't noticeable
- RussianCow 8y ago
  Frame drops that happen more than once every several seconds are definitely noticeable (and, as a sibling comment pointed out, especially so in VR). Plus, throwing away more than half your frame budget just because of GC seems unreasonable. And this isn't even considering monitors with high refresh rates, which are slowly getting more and more popular.
- blattimwind 8y ago
  > When games load in assets they'll do various things like malloc huge chunks and you lose a few frames. Streaming/Loading assets in the main render thread is a very 2005 thing to do.
  - vvanders 8y ago
    Yeah, the whole reason you have pools and arena allocators is so that you don't do small/large malloc mid-frame. Perf 101 is don't malloc during regular gameplay.
- barrkel 8y ago
  Quake, back in the late 90s, would preload assets for all entities in a level at level load time explicitly to avoid stutter when the entity finally shows up and needs to make a noise or whatever. And some games much later didn't. I recall needing to fire off a shot on each new gun I picked up in Far Cry to be sure I wouldn't get a stutter later at a more critical moment.
deleted 8y ago
[deleted]
pron 8y ago
ZGC, included in JDK 11, has a 1ms average pause time and 4ms max on some demanding benchmarks, and they're now targeting 1ms max pauses. https://www.opsian.com/blog/javas-new-zgc-is-very-exciting/ https://www.opsian.com/blog/javas-new-zgc-is-very-exciting/
- spricket 8y ago
  Wow great link. I live pretty deep in Javaland and had no idea it was that good!
- gigatexal 8y ago
  If it lives up to claims surely it’s a paid for add on?
  - pron 8y ago
    Originally it was intended as a commercial feature, but since JDK 11 Oracle open sourced all previously-commercial features in the JDK, and now it's part of OpenJDK. It's already available in JDK 11 and 12.
    - gigatexal 8y ago
      I never got to the level where I needed anything more than the stock default GC. But this looks compelling. Does Kotlin and other JVM based languages benefit from it, too?
      - pron 8y ago
        Sure. All languages that run on the Java platform[1] can benefit from it, and from most other Java platform enhancements. [1]: I prefer saying Java platform rather than JVM, because a program written in Kotlin shares over 90% of its infrastructure code with a program written in Java (not including the OS), and the JVM constitutes only about 20% of that.
  - karussell 8y ago
    It works really great with heaps >100GB and is included in the openjdk since 11. Note, that only linux is supported, I think
AnIdiotOnTheNet 8y ago
16ms is only if you're just targeting 60fps. We now have 144hz monitors, leaving less than half of that if you want to take full advantage of the hardware.
jtolmar 8y ago
If you have some control over when a GC triggers you could sneak one in during hitstun.
CaptainJustin 8y ago
A few of us built a webgl game backend in Java. It was fun but optimizing to make everything always work within 16ms was hard. In our case it was especially complicated because we shared state over websockets back to the clients.

In VR your budget is 11 ms and you can't miss it or the entire frame is thrown away and you introduce a frame of latency to compensate. So for VR these kind of effects of GC are even worse.

chipperyman573 8y ago
Also, while most games are fine with losing a frame or two every few minutes, in VR dropping frames will cause motion sickness really fast. FPS is, from what I've observed, the most important part of a VR game. If you're dropping frames or stuttering, the experience will suffer greatly When I was developing a VR game, my team noticed that some ultra-sensitive people started to get sick when we would drop around five frames (the vive displays 90, so this is only a ~5% drop). There was more to it (dropping a few frames every few minutes was usually fine, but consistently dropping frames every second or two is an issue).

spricket 8y ago

10 ms isn't all that much. When games load in assets they'll do various things like malloc huge chunks and you lose a few frames. If GC only causes occasional (maybe every 2 minutes) loss of a frame or two it should be no problem. If you watch benchmark FPS traces that count every frame delay you'll see that occasional stutters happen in basically every game. Loss of a single frame just isn't noticeable

RussianCow 8y ago
Frame drops that happen more than once every several seconds are definitely noticeable (and, as a sibling comment pointed out, especially so in VR). Plus, throwing away more than half your frame budget just because of GC seems unreasonable. And this isn't even considering monitors with high refresh rates, which are slowly getting more and more popular.
blattimwind 8y ago
> When games load in assets they'll do various things like malloc huge chunks and you lose a few frames. Streaming/Loading assets in the main render thread is a very 2005 thing to do.
- vvanders 8y ago
  Yeah, the whole reason you have pools and arena allocators is so that you don't do small/large malloc mid-frame. Perf 101 is don't malloc during regular gameplay.
barrkel 8y ago
Quake, back in the late 90s, would preload assets for all entities in a level at level load time explicitly to avoid stutter when the entity finally shows up and needs to make a noise or whatever. And some games much later didn't. I recall needing to fire off a shot on each new gun I picked up in Far Cry to be sure I wouldn't get a stutter later at a more critical moment.

deleted 8y ago

[deleted]

pron 8y ago

ZGC, included in JDK 11, has a 1ms average pause time and 4ms max on some demanding benchmarks, and they're now targeting 1ms max pauses. https://www.opsian.com/blog/javas-new-zgc-is-very-exciting/ https://www.opsian.com/blog/javas-new-zgc-is-very-exciting/

spricket 8y ago
Wow great link. I live pretty deep in Javaland and had no idea it was that good!
gigatexal 8y ago
If it lives up to claims surely it’s a paid for add on?
- pron 8y ago
  Originally it was intended as a commercial feature, but since JDK 11 Oracle open sourced all previously-commercial features in the JDK, and now it's part of OpenJDK. It's already available in JDK 11 and 12.
  - gigatexal 8y ago
    I never got to the level where I needed anything more than the stock default GC. But this looks compelling. Does Kotlin and other JVM based languages benefit from it, too?
    - pron 8y ago
      Sure. All languages that run on the Java platform[1] can benefit from it, and from most other Java platform enhancements. [1]: I prefer saying Java platform rather than JVM, because a program written in Kotlin shares over 90% of its infrastructure code with a program written in Java (not including the OS), and the JVM constitutes only about 20% of that.
- karussell 8y ago
  It works really great with heaps >100GB and is included in the openjdk since 11. Note, that only linux is supported, I think

AnIdiotOnTheNet 8y ago

16ms is only if you're just targeting 60fps. We now have 144hz monitors, leaving less than half of that if you want to take full advantage of the hardware.

jtolmar 8y ago

If you have some control over when a GC triggers you could sneak one in during hitstun.

CaptainJustin 8y ago

A few of us built a webgl game backend in Java. It was fun but optimizing to make everything always work within 16ms was hard. In our case it was especially complicated because we shared state over websockets back to the clients.