runtime: overestimate the amount of allocated memory in heapLive
CL 377516 made it so that memory metrics are truly monotonic, but also
updated how heapLive tracked allocated memory to also be monotonic.
The result is that cached spans with allocated memory aren't fully
accounted for by the GC, causing it to make a worse assumption (the
exact mechanism is at this time unknown), resulting in a memory
regression, especially for smaller heaps.
This change is a partial revert of CL 377516 that makes heapLive a
non-monotonic overestimate again, which appears to resolve the
regression.
For #53738.
Change-Id: I5c51067abc0b8e0a6b89dd8dbd4a0be2e8c0c1b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/416417 Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>