Currently, it is started/stopped in the streaming/maintenance sg, which
is what the API itself runs in.
Starting the native transport in the streaming sg, will lead to severely
degraded performance, as the streaming sg has significantly less
CPU/disk shares and reader concurrency semaphore resources.
Furthermore, it will lead to multi-paged reads possibly switching
between scheduling groups mid-way, triggering an internal error.
To fix, use `with_scheduling_group()` for both starting and stopping
native transport. Technically, it is only strictly necessary for
starting, but I added it for stop as well for consistency.
Also apply the same treatment to RPC (Thrift). Although no one uses it,
best to fix it, just to be on the safe side.
I think we need a more systematic approach for solving this once and for
all, like passing the scheduling group to the protocol server and have
it switch to it internally. This allows the server to always run on the
correct scheduling group, not depending on the caller to remember using
it. However, I think this is best done in a follow-up, to keep this
critical patch small and easily backportable.
Fixes: #15485Closesscylladb/scylladb#16019
dfd7981fa7