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Proposal: Soft memory limit

Author: Michael Knyszek

Summary

I propose a new option for tuning the behavior of the Go garbage collector by setting a soft memory limit on the total amount of memory that Go uses.

This option comes in two flavors: a new runtime/debug function called SetMemoryLimit and a GOMEMLIMIT environment variable. In sum, the runtime will try to maintain this memory limit by limiting the size of the heap, and by returning memory to the underlying platform more aggressively. This includes with a mechanism to help mitigate garbage collection death spirals. Finally, by setting GOGC=off, the Go runtime will always grow the heap to the full memory limit.

This new option gives applications better control over their resource economy. It empowers users to:

Better utilize the memory that they already have,
Confidently decrease their memory limits, knowing Go will respect them,
Avoid unsupported forms of garbage collection tuning.

Details

Full design document found here.

Note that, for the time being, this proposal intends to supersede #44309. Frankly, I haven't been able to find a significant use-case for it, as opposed to a soft memory limit overall. If you believe you have a real-world use-case for a memory target where a memory limit with GOGC=off would not solve the same problem, please do not hesitate to post on that issue, contact me on the gophers slack, or via email at mknyszek@golang.org. Please include as much detail as you can.