The JSHeap varries from 24.4MB to 25.5MB, so a 1.1MB heap memory is being cleared once in a while. We do our best to reuse elements and never recreate them (thou it is sometimes impossible). This 1.1MB can come from the browser itself or some other js scripts running in the background (the editor, for example).
Examining a more complex scene (for example) https://playground.babylonjs.com/#3VMTI9#0 will give you the same memory span (ca. 1MB), which is somewhat acceptable.
Also notice the amount of idle time the performance report is showing. There should not be any lag at all. Do you get a lag with the default scene? or with a more complex one? wanna share a screencast? or better yet - a playground?
** EDIT - if you do however find some place where we don’t reuse objects, we will fix it ASAP