rcu: Remove TINY_RCU bloat from pointless boot parameters

The rcu_expedited, rcu_normal, and rcu_normal_after_boot kernel boot
parameters are pointless in the case of TINY_RCU because in that case
synchronous grace periods, both expedited and normal, are no-ops.
However, these three symbols contribute several hundred bytes of bloat.
This commit therefore uses CPP directives to avoid compiling this code
in TINY_RCU kernels.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 197305bbb9b7..d8186da15ca1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3308,20 +3308,23 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			of synchronize_rcu().  This reduces latency,
 			but can increase CPU utilization, degrade
 			real-time latency, and degrade energy efficiency.
+			No effect on CONFIG_TINY_RCU kernels.
 
 	rcupdate.rcu_normal= [KNL]
 			Use only normal grace-period primitives,
 			for example, synchronize_rcu() instead of
 			synchronize_rcu_expedited().  This improves
-			real-time latency, CPU utilization, and energy
-			efficiency, but can expose users to increased
-			grace-period latency.  This parameter overrides
-			rcupdate.rcu_expedited.
+			real-time latency, CPU utilization, and
+			energy efficiency, but can expose users to
+			increased grace-period latency.  This parameter
+			overrides rcupdate.rcu_expedited.  No effect on
+			CONFIG_TINY_RCU kernels.
 
 	rcupdate.rcu_normal_after_boot= [KNL]
 			Once boot has completed (that is, after
 			rcu_end_inkernel_boot() has been invoked), use
-			only normal grace-period primitives.
+			only normal grace-period primitives.  No effect
+			on CONFIG_TINY_RCU kernels.
 
 	rcupdate.rcu_task_stall_timeout= [KNL]
 			Set timeout in jiffies for RCU task stall warning