Commits on Dec 21, 2023

1. Make Bazel's RAM estimate container aware …

   As of JDK 14, `OperatingSystemMXBean` provides information about system memory that is container-aware. Outside containers, it uses the same mechanisms as Bazel to determine available RAM (`/proc/meminfo` on Linux, `hw.memsize` on macOS) and can thus be used as a drop-in replacement for the custom implementation.
   
   A small caveat is that Bazel's macOS RAM estimate was based on converting bytes to "MB" via a divisor of `1000^2` instead of `1024^2`, resulting in a consistent overestimate compared to an identical Linux machine that is now corrected.
   
   This opportunity was missed in bazelbuild#16512 since `OperatingSystemMXBean` is based on a complete Java implementation of cgroups handling and doesn't go through the `os::total_memory` or `os::physical_memory` Hotspot functions.
   
   RELNOTES[INC]:
   * On Linux, Bazel's RAM estimate for the host machine is now aware of container resource limits.
   * On macOS, Bazel no longer consistently overestimates the total RAM by ~5% (`1024^2/1000^2`).
   * On Windows, Bazel's RAM estimate is now generally more accurate as it is no longer influenced by JVM heuristics.
   
   Fixes bazelbuild#3886
   
   Closes bazelbuild#20435.
   
   PiperOrigin-RevId: 588718034
   Change-Id: I2daafa0567740a1b149ca8756ec27f102129283c

   

   fmeum authored and bazel-io committed Dec 21, 2023
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