rcu: Add shrinker to shift to fast/inefficient GP mode
This commit adds a shrinker so as to inform RCU when memory is scarce.
RCU responds by shifting into the same fast and inefficient mode that is
used in the presence of excessive numbers of RCU callbacks. RCU remains
in this state for one-tenth of a second, though this time window can be
extended by another call to the shrinker.
If it proves feasible, a later commit might add a function call directly
indicating the end of the period of scarce memory.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
2 files changed
