1510560 - Use a more intelligent pretenure condition

Status: RESOLVED DUPLICATE of bug 1700291

(Core :: JavaScript: GC, enhancement, P3)

Description

[Paul Bone [:pbone]]

If over 60% of the nursery is tenured, then the nursery will check each object group to see if it should be pretenured.  This condition isn't ideal when the nursery is small and we're somewhat likely tio have a high tenure rate.  We can avoid some agressive pretenuring just by adding the condition that the nursery is also 4MB or larger.  But we should try to do something even more inteligent than that.

Jonco suggested we don't pretenuring any time we're also going to grow the nursery.  But since that is also threshold based, and a lower threashold, we'd never pretenure into the nursery was already 16MB big (up to four collections later), which may be not agressive enough.