diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-02-03 09:27:00 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-03-16 14:06:01 -0700 |
| commit | c74ba39b5b87d59cfa642643be7c6cd23ea3ca3b (patch) | |
| tree | 997d5bc9c756fbee6e2d7a8375c739a8a52e9c15 /init | |
| parent | 4a264dfacfa0ac6f10a0718aaff2076ad432230e (diff) | |
rcu: Make RCU_FANOUT_LEAF help text more explicit about skew_tick
If you set RCU_FANOUT_LEAF too high, you can get lock contention
on the leaf rcu_node, and you should boot with the skew_tick kernel
parameter set in order to avoid this lock contention. This commit
therefore upgrades the RCU_FANOUT_LEAF help text to explicitly state
this.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'init')
| -rw-r--r-- | init/Kconfig | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/init/Kconfig b/init/Kconfig index a92f27da4a27..c859c993c26f 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -612,11 +612,15 @@ config RCU_FANOUT_LEAF initialization. These systems tend to run CPU-bound, and thus are not helped by synchronized interrupts, and thus tend to skew them, which reduces lock contention enough that large - leaf-level fanouts work well. + leaf-level fanouts work well. That said, setting leaf-level + fanout to a large number will likely cause problematic + lock contention on the leaf-level rcu_node structures unless + you boot with the skew_tick kernel parameter. Select a specific number if testing RCU itself. - Select the maximum permissible value for large systems. + Select the maximum permissible value for large systems, but + also boot with the skew_tick kernel parameter set. Take the default if unsure. |