Commit cf244dc0 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: default avatarJosh Triplett <josh@joshtriplett.org>
Acked-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
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: default avatarIngo Molnar <mingo@elte.hu>
parent d3f6bad3

kernel/rcutree.c

+5 −1
Original line number Original line Diff line number Diff line
@@ -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_0,  /* root of hierarchy. */ \

		NUM_RCU_LVL_1, \

		NUM_RCU_LVL_1, \

		NUM_RCU_LVL_2, \

		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, \

	.signaled = RCU_GP_IDLE, \

	.gpnum = -300, \

	.gpnum = -300, \
@@ -1877,6 +1878,9 @@ void __init rcu_init(void) 
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

#ifdef CONFIG_RCU_CPU_STALL_DETECTOR

	printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");

	printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");

#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */

#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_sched_state, rcu_sched_data);

	RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data);

	RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data);

	__rcu_init_preempt();

	__rcu_init_preempt();

kernel/rcutree.h

+13 −2
Original line number Original line Diff line number Diff line
@@ -34,10 +34,11 @@ 
 * In practice, this has not been tested, so there is probably some

 * In practice, this has not been tested, so there is probably some

 * bug somewhere.

 * bug somewhere.

 */

 */

#define MAX_RCU_LVLS 3

#define MAX_RCU_LVLS 4

#define RCU_FANOUT	      (CONFIG_RCU_FANOUT)

#define RCU_FANOUT	      (CONFIG_RCU_FANOUT)

#define RCU_FANOUT_SQ	      (RCU_FANOUT * RCU_FANOUT)

#define RCU_FANOUT_SQ	      (RCU_FANOUT * RCU_FANOUT)

#define RCU_FANOUT_CUBE	      (RCU_FANOUT_SQ * 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

#if NR_CPUS <= RCU_FANOUT

#  define NUM_RCU_LVLS	      1

#  define NUM_RCU_LVLS	      1
@@ -45,23 +46,33 @@ 
#  define NUM_RCU_LVL_1	      (NR_CPUS)

#  define NUM_RCU_LVL_1	      (NR_CPUS)

#  define NUM_RCU_LVL_2	      0

#  define NUM_RCU_LVL_2	      0

#  define NUM_RCU_LVL_3	      0

#  define NUM_RCU_LVL_3	      0

#  define NUM_RCU_LVL_4	      0

#elif NR_CPUS <= RCU_FANOUT_SQ

#elif NR_CPUS <= RCU_FANOUT_SQ

#  define NUM_RCU_LVLS	      2

#  define NUM_RCU_LVLS	      2

#  define NUM_RCU_LVL_0	      1

#  define NUM_RCU_LVL_0	      1

#  define NUM_RCU_LVL_1	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)

#  define NUM_RCU_LVL_1	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)

#  define NUM_RCU_LVL_2	      (NR_CPUS)

#  define NUM_RCU_LVL_2	      (NR_CPUS)

#  define NUM_RCU_LVL_3	      0

#  define NUM_RCU_LVL_3	      0

#  define NUM_RCU_LVL_4	      0

#elif NR_CPUS <= RCU_FANOUT_CUBE

#elif NR_CPUS <= RCU_FANOUT_CUBE

#  define NUM_RCU_LVLS	      3

#  define NUM_RCU_LVLS	      3

#  define NUM_RCU_LVL_0	      1

#  define NUM_RCU_LVL_0	      1

#  define NUM_RCU_LVL_1	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ)

#  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_2	      DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)

#  define NUM_RCU_LVL_3	      NR_CPUS

#  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

#else

# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"

# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"

#endif /* #if (NR_CPUS) <= RCU_FANOUT */

#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)

#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)





/*

/*

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