node only using half of the available memory

• Version: 12.19.0
• Platform: Debian Buster
• Subsystem:

What steps will reproduce the bug?

1. Start a container with limited memory (something like docker run --rm -it --memory=1G --memory-swap=1G node:12.19.0-buster-slim bash
2. Inspect heap size (node -e 'const v8 = require("v8"); console.log(v8.getHeapStatistics());')

How often does it reproduce? Is there a required condition?

100%

What is the expected behavior?

node would use all available memory

What do you see instead?

node is only using half of the memory, so we either need to give the container twice as much memory as we really want it to use (which is problematic) or also specify --max-old-space-size in addition to controlling the container which means we have to keep 2 different settings in sync and that's a big pain

Additional information

It appears that it was changed here, and only using half of memory makes sense when running on a system with multiple process, but when running in a docker container, using all of the memory allocated to the container makes more sense

まず、提供された docker run コマンドと node -e v8.getHeapStatistics() の確認を使って問題を再現します。Node.js がコンテナのメモリ上限をどのように判定しているかを追跡し、その値を想定される 1G の割り当てと比較します。完了の条件は、別途 --max-old-space-size を設定しなくても、ランタイムがヒープを適切なサイズに設定することです。