TYPO3 Core

The memcache Backend is very slow if entries with a lot of tags are handled.

Use case:
We have pages that need around 150 tags assigned to a page cache entry. cache->set() in tsfe takes around 3 seconds (!) to write the entry to memcache backend.
Most of this time is eaten up in t3lib_cache_backend_MemcachedBackend->addIdentifierToTags() where identifier<->tag entries are handled.

APC backend seems to use the same logic as memcached, so both are currently unusable if many tags are handled, dbbackend is much quicker in this case (but could be optimized in set() too, if it would INSERT all tag entries at once and not in a loop for each tag).

(issue imported from #M12562)