3 ms·

Are there any production-ready GCs that have strictly bounded latency? I'm not aware of any, and that means that GC is still too immature for use in about 95% o

by addaon 4y ago

Are there any production-ready GCs that have strictly bounded latency? I'm not aware of any, and that means that GC is still too immature for use in about 95% of the computers in my house, the deeply embedded ones.

mike_hearn 4y ago
Metronome did this for embedded hard realtime use cases. I don't know much about it. ZGC has bounded pause latency at least but it's not really meant for very small machines. Android has used a pauseless GC for a while.
kaba0 4y ago
Strictly bounded anything (hard real-time) is an entirely different category, with very few uses for the average person - and contrary to what one might think from its name, it is not “fast” at all. It’s mostly about “calculating the trajectory of that incoming projectile should definitely happen in 0.3s”, which is many orders of magnitude more than what a modern computer would take to do 3 multiplications. But to answer your question, there is JamaicaVM and many niche JVM implementations with hard real time GCs — but it’s simply false that a GC would be somehow a problem for most of your devices.
- addaon 4y ago
  Hard real-time has a huge amount of uses for the average person. I just made toast -- the software-controlled thermostat in my toaster oven has (slow) hard bounds on its sense-to-control latency to avoid dangerous overheating. Before that, I brushed my teeth -- the brushed motor controller detects a motor stall by increased current if I brush too hard and stall it, shuts down the motor to avoid overheating (with a hard real-time sense-to-actuate constraint), and beeps to inform me. Then I spent some time on HN, with a laptop with PMICs and other microcontrollers that have hard real-time constraints all over the place. By far the majority of my computer interactions so far today have been with computers that have hard real-time constraints, and I haven't even gotten in my car yet!

by addaon 4y ago

mike_hearn 4y ago

Metronome did this for embedded hard realtime use cases. I don't know much about it. ZGC has bounded pause latency at least but it's not really meant for very small machines. Android has used a pauseless GC for a while.

kaba0 4y ago

Strictly bounded anything (hard real-time) is an entirely different category, with very few uses for the average person - and contrary to what one might think from its name, it is not “fast” at all. It’s mostly about “calculating the trajectory of that incoming projectile should definitely happen in 0.3s”, which is many orders of magnitude more than what a modern computer would take to do 3 multiplications. But to answer your question, there is JamaicaVM and many niche JVM implementations with hard real time GCs — but it’s simply false that a GC would be somehow a problem for most of your devices.

addaon 4y ago
Hard real-time has a huge amount of uses for the average person. I just made toast -- the software-controlled thermostat in my toaster oven has (slow) hard bounds on its sense-to-control latency to avoid dangerous overheating. Before that, I brushed my teeth -- the brushed motor controller detects a motor stall by increased current if I brush too hard and stall it, shuts down the motor to avoid overheating (with a hard real-time sense-to-actuate constraint), and beeps to inform me. Then I spent some time on HN, with a laptop with PMICs and other microcontrollers that have hard real-time constraints all over the place. By far the majority of my computer interactions so far today have been with computers that have hard real-time constraints, and I haven't even gotten in my car yet!