Truncate uses RPC timeout, which is in my case set to 10 seconds (I want even less) and it's not enough. I've seen in sources TODO for this case.
What I found is that truncate starting flush for all memtables for all CFs, not only for a CF to be truncated. When there're a lot of CFs to be flushed, it takes time.
Is it possible to flush only required CF for truncate, not all? This could improve truncate time.