On Wed, Nov 16, 2016 at 05:35:47PM -0800, Junio C Hamano wrote: > OK, here is what I have queued. > > -- >8 -- > Subject: cache-tree: make sure to "touch" tree objects the cache-tree records > > The cache_tree_fully_valid() function is called by callers that want > to know if they need to call cache_tree_update(), i.e. as an attempt > to optimize. They all want to have a fully valid cache-tree in the > end so that they can write a tree object out.
That makes sense. I was focusing on cache_tree_update() call, but we do not even get there in the fully-valid case. So I think this approach is nice as long as there is not a caller who asks "are we fully valid? I do not need to write, but was just wondering". That should be a read-only operation, but the freshen calls may fail with EPERM, for example. I do not see any such callers, nor do I really expect any. Just trying to think through the possible consequences. > Strictly speaking, freshing these tree objects at each and every > level is probably unnecessary, given that anything reachable from a > young object inherits the youth from the referring object to be > protected from pruning. It should be sufficient to freshen only the > very top-level tree instead. Benchmarking and optimization is left > as an exercise for later days. Good observation, and nicely explained all around. -Peff
