Enable Setting TCMalloc Soft Memory Limit

[ryansmick]

Title: Enable Setting TCMalloc Soft Memory Limit

Description:
Google’s TCMalloc offers the ability to set a soft memory limit in code. It works by attempting to release pages from the Page Heap if a new allocation from the OS puts tcmalloc’s total memory footprint above the soft limit. For users of Google’s TCMalloc, this seems to be an alternative to the shrink_heap action in overload manager, and we’d like to evaluate it as such.

It seems the only way to set this limit in TCMalloc is to call this function, and I don’t see any calls of this in envoy. Would it be possible to update envoy to support setting this soft limit in TCMalloc, perhaps via a bootstrap configuration or an environment variable?

[tyxia]

Add @nezdolik who has worked on this a lot in the past, IIRC

[nezdolik]

Sounds like a reasonable feature, we could extend MemoryAllocatorManager api for this.