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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-12-07 13:09:52 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-12-07 16:59:37 -0800 |
| commit | 79cfea0273876d9c438f3227b8f68c8c7ae31583 (patch) | |
| tree | b147a1c382fd50ac1ee5113ea851b517bf3405df /Documentation/kernel-parameters.txt | |
| parent | 3e42ec1aa716f10c68294b8492ae3ea684528699 (diff) | |
| download | lwn-79cfea0273876d9c438f3227b8f68c8c7ae31583.tar.gz lwn-79cfea0273876d9c438f3227b8f68c8c7ae31583.zip | |
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>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
| -rw-r--r-- | Documentation/kernel-parameters.txt | 13 |
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 |