Rebuilding discourse when executing some place, my server will be a lot of lag

Installation
1

When the build is executed to print “Node.js heap_size_limit (888.75) is less than 2048MB. Setting --max-old-space-size=2048 and CHEAP_SOURCE_MAPS=1” servre will be a lot of lag, why? and i wait it over 1 hours…it’s useless…