lock contention - what can we do about it?

[David Nolden]

No, it cannot be rewritten like this, because the mutex also ensures
the integrity of the whole repository dataRepository, and you must not
call methods like dynamicItemFromIndexSimple without holding it.

AFAIR, dataRepository has all its own thread-safety disabled, and is
protected by a "higher" surrounding mutex, which is
m_repository->m_mutex, that's why that mutex is used.