This patch changes the layout of user-facing scheduling groups from
/
`- statement
`- sl:default
`- sl:*
`- other groups (compaction, streaming, etc.)
into
/
`- user (supergroup)
`- statement
`- sl:default
`- sl:*
`- other groups (compaction, streaming, etc.)
The new supergroup has 1000 static shares and is name-less, in a sense
that it only have a variable in the code to refer to and is not exported
via metrics (should be fixed in seastar if we want to).
The moved groups don't change their names or shares, only move inside
the scheduling hierarchy.
The goal of the change is to improve resource consumption of sl:*
groups. Right now activities in low-shares service levels are scheduled
on-par with e.g. streaming activity, which is considered to be low-prio
one. By moving all sl:* groups into their own supergroup with 1000
shares changes the meaning of sl:* shares. From now on these shares
values describe preirities of service level between each-other, and the
user activities compete with the rest of the system with 1000 shares,
regardless of how many service levels are there.
Unit tests keep their user groups under root supergroup (for simplicity)
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closesscylladb/scylladb#28235
18b5a49b0c