From: Kunwu Chan <[email protected]> Add explicit explanations of the overall purpose of RCU_FANOUT and RCU_FANOUT_LEAF parameters: defining middle/leaf fan-out parameters, their relation to Kconfig, and how they shape the RCU hierarchy based on CPU count.
This makes the hierarchical configuration logic of the RCU easier to understand. Signed-off-by: Kunwu Chan <[email protected]> --- Changes in v2: - Restores the original #else #endif comment format - Reword commit msg --- include/linux/rcu_node_tree.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/linux/rcu_node_tree.h b/include/linux/rcu_node_tree.h index 78feb8ba7358..a87ca215de4b 100644 --- a/include/linux/rcu_node_tree.h +++ b/include/linux/rcu_node_tree.h @@ -25,11 +25,18 @@ /* * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and * CONFIG_RCU_FANOUT_LEAF. + * - RCU_FANOUT: Controls fan-out of middle levels in the RCU hierarchy. + * - RCU_FANOUT_LEAF: Controls fan-out of the leaf level (directly managing CPUs). + * + * These parameters are determined by Kconfig options if configured; otherwise, + * they use sensible defaults based on system architecture (for RCU_FANOUT) + * or a fixed default (for RCU_FANOUT_LEAF). * In theory, it should be possible to add more levels straightforwardly. * In practice, this did work well going from three levels to four. * Of course, your mileage may vary. */ +/* Define RCU_FANOUT: middle-level fan-out parameter */ #ifdef CONFIG_RCU_FANOUT #define RCU_FANOUT CONFIG_RCU_FANOUT #else /* #ifdef CONFIG_RCU_FANOUT */ @@ -40,6 +47,7 @@ # endif #endif /* #else #ifdef CONFIG_RCU_FANOUT */ +/* Define RCU_FANOUT_LEAF: leaf-level fan-out parameter (manages CPUs directly) */ #ifdef CONFIG_RCU_FANOUT_LEAF #define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF #else /* #ifdef CONFIG_RCU_FANOUT_LEAF */ -- 2.25.1
