srcu: Add boot-time control over srcu_node array allocation

This commit adds an srcu_tree.convert_to_big kernel parameter that either
refuses to convert at all (0), converts immediately at init_srcu_struct()
time (1), or lets rcutorture convert it (2).  An addition contention-based
dynamic conversion choice will be added, along with documentation.

[ paulmck: Apply callback-scanning feedback from Neeraj Upadhyay. ]

Co-developed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-01-25 15:41:10 -08:00
parent 0b56f95390
commit c69a00a12e
2 changed files with 45 additions and 16 deletions

View file

@ -5608,6 +5608,19 @@
off: Disable mitigation and remove
performance impact to RDRAND and RDSEED
srcutree.convert_to_big [KNL]
Specifies under what conditions an SRCU tree
srcu_struct structure will be converted to big
form, that is, with an rcu_node tree:
0: Never.
1: At init_srcu_struct() time.
2: When rcutorture decides to.
Either way, the srcu_node tree will be sized based
on the actual runtime number of CPUs (nr_cpu_ids)
instead of the compile-time CONFIG_NR_CPUS.
srcutree.counter_wrap_check [KNL]
Specifies how frequently to check for
grace-period sequence counter wrap for the