From 79cfea0273876d9c438f3227b8f68c8c7ae31583 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 7 Dec 2015 13:09:52 -0800 Subject: 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 Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- Documentation/kernel-parameters.txt | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'Documentation/kernel-parameters.txt') 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 -- cgit v1.2.3