A Linux machine typically has multiple clocksources with distinct
performances. Setting a high-performant clocksource might result in
better performance for ScyllaDB, so this should be considered whenever
starting it up.
This patch introduces the possibility of enforcing optimized Linux
clocksource to Scylla's setup/start-up processes. It does so by adding
an interactive question about enforcing clocksource setting to scylla_setup,
which modifies the parameter "CLOCKSOURCE" in scylla_server configuration
file. This parameter is read by perftune.py which, if set to "yes", proceeds
to (non persistently) setting the clocksource. On x86, TSC clocksource is used.
Fixes#4474Fixes#5474Fixes#5480
d7795b1efa