Cannot free up memory used by entryCache in Modules

[sengleung]

entryCache is instantiated by Modules

goyang/pkg/yang/modules.go

Lines 35 to 37 in a34098e

	// entryCache is used to prevent unnecessary recursion into previously
	// converted nodes.
	entryCache map[Node]*Entry

and is used only by the ToEntry function.

goyang/pkg/yang/entry.go

Lines 562 to 567 in a34098e

	if e := ms.entryCache[n]; e != nil {
	return e
	}
	defer func() {
	ms.entryCache[n] = e
	}()

entryCache in Modules can take up a bit of amount of memory after processing all YANG modules. For our use case, after processing all YANG modules, calls to ToEntry, which accesses the entryCache, happen very infrequently, if at all. Therefore, it is ideal to clear the cache to free up memory.

I don't think this should not compromise on correctness. Even if entryCache is cleared, calling ToEntry will just recurse and cache the relevant nodes again.

Issue #248 also refers to this issue. Creating this issue as this relates only to entryCache.