[TYPO3-core] RFC: #11271: Use 2 level cache for BEgetRootLine

[Steffen Kamper]

Hi,

here is an updated patch that takes care of clearing the cache when 
move/create/delete/update a page, also if you switch the BE language.

In my local test environment i have 3-4 calls to BEgetRootLine each page 
hit.

The time needed for processing the rootline is
without cache: 25-80ms each hit
with 1st level cache: 0.02-0.05 ms
with 2nd level cache: 0.2-0.5 ms

without patch i have each page hit
2 calls not cached = 80-120 ms
2 calls 1st level cache ~ 0.06 ms

with patch i have each cached page hit
2 calls 2nd level cache ~ 0.7 ms
2 calls 1st level cache ~ 0.06 ms

so imho it's a good performance boost.

vg Steffen