From cf244dc01bf68e1ad338b82447f8686d24ea4435 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 2 Dec 2009 12:10:14 -0800 Subject: [PATCH] rcu: Enable fourth level of TREE_RCU hierarchy Enable a fourth level of rcu_node hierarchy for TREE_RCU and TREE_PREEMPT_RCU. This is for stress-testing and experiemental purposes only, although in theory this would enable 16,777,216 CPUs on 64-bit systems, though only 1,048,576 CPUs on 32-bit systems. Normal experimental use of this fourth level will normally set CONFIG_RCU_FANOUT=2, requiring a 16-CPU system, though the more adventurous (and more fortunate) experimenters may wish to chose CONFIG_RCU_FANOUT=3 for 81-CPU systems or even CONFIG_RCU_FANOUT=4 for 256-CPU systems. Signed-off-by: Paul E. McKenney Acked-by: Josh Triplett Acked-by: Lai Jiangshan Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <12597846161257-git-send-email-> Signed-off-by: Ingo Molnar --- kernel/rcutree.c | 6 +++++- kernel/rcutree.h | 15 +++++++++++++-- 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index a9f51031d3e8..d47e03e5792a 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -60,7 +60,8 @@ static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; NUM_RCU_LVL_0, /* root of hierarchy. */ \ NUM_RCU_LVL_1, \ NUM_RCU_LVL_2, \ - NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \ + NUM_RCU_LVL_3, \ + NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ }, \ .signaled = RCU_GP_IDLE, \ .gpnum = -300, \ @@ -1877,6 +1878,9 @@ void __init rcu_init(void) #ifdef CONFIG_RCU_CPU_STALL_DETECTOR printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ +#if NUM_RCU_LVL_4 != 0 + printk(KERN_INFO "Experimental four-level hierarchy is enabled.\n"); +#endif /* #if NUM_RCU_LVL_4 != 0 */ RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); __rcu_init_preempt(); diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 8bb03cb07447..df2e0b694744 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -34,10 +34,11 @@ * In practice, this has not been tested, so there is probably some * bug somewhere. */ -#define MAX_RCU_LVLS 3 +#define MAX_RCU_LVLS 4 #define RCU_FANOUT (CONFIG_RCU_FANOUT) #define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT) #define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT) +#define RCU_FANOUT_FOURTH (RCU_FANOUT_CUBE * RCU_FANOUT) #if NR_CPUS <= RCU_FANOUT # define NUM_RCU_LVLS 1 @@ -45,23 +46,33 @@ # define NUM_RCU_LVL_1 (NR_CPUS) # define NUM_RCU_LVL_2 0 # define NUM_RCU_LVL_3 0 +# define NUM_RCU_LVL_4 0 #elif NR_CPUS <= RCU_FANOUT_SQ # define NUM_RCU_LVLS 2 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) # define NUM_RCU_LVL_2 (NR_CPUS) # define NUM_RCU_LVL_3 0 +# define NUM_RCU_LVL_4 0 #elif NR_CPUS <= RCU_FANOUT_CUBE # define NUM_RCU_LVLS 3 # define NUM_RCU_LVL_0 1 # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ) # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) # define NUM_RCU_LVL_3 NR_CPUS +# define NUM_RCU_LVL_4 0 +#elif NR_CPUS <= RCU_FANOUT_FOURTH +# define NUM_RCU_LVLS 4 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_CUBE) +# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ) +# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) +# define NUM_RCU_LVL_4 NR_CPUS #else # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" #endif /* #if (NR_CPUS) <= RCU_FANOUT */ -#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) +#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4) #define NUM_RCU_NODES (RCU_SUM - NR_CPUS) /* -- 2.20.1