[PATCH v3 4/9] rcu: Simplify rcu_init_geometry() capacity arithmetics
Current code suggests that introducing the extra level to rcu_capacity[] array makes some of the arithmetic easier. Well, in fact it appears rather confusing and unnecessary. Cc: "Paul E. McKenney" Cc: Steven Rostedt Signed-off-by: Alexander Gordeev --- kernel/rcu/tree.c | 18 -- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 79c91d4..fb5a4cb 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4082,7 +4082,7 @@ static void __init rcu_init_geometry(void) { ulong d; int i; - int rcu_capacity[MAX_RCU_LVLS + 1]; + int rcu_capacity[MAX_RCU_LVLS]; /* * Initialize any unspecified boot parameters. @@ -4119,29 +4119,27 @@ static void __init rcu_init_geometry(void) /* * Compute number of nodes that can be handled an rcu_node tree -* with the given number of levels. Setting rcu_capacity[0] makes -* some of the arithmetic easier. +* with the given number of levels. */ - rcu_capacity[0] = 1; - rcu_capacity[1] = rcu_fanout_leaf; - for (i = 2; i <= MAX_RCU_LVLS; i++) + rcu_capacity[0] = rcu_fanout_leaf; + for (i = 1; i < MAX_RCU_LVLS; i++) rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT; /* * The tree must be able to accommodate the configured number of CPUs. * If this limit is exceeded than we have a serious problem elsewhere. */ - if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS]) + if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS - 1]) panic("rcu_init_geometry: rcu_capacity[] is too small"); /* Calculate the number of levels in the tree. */ - for (i = 1; nr_cpu_ids > rcu_capacity[i]; i++) { + for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) { } - rcu_num_lvls = i; + rcu_num_lvls = i + 1; /* Calculate the number of rcu_nodes at each level of the tree. */ for (i = 0; i < rcu_num_lvls; i++) { - int cap = rcu_capacity[rcu_num_lvls - i]; + int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); } -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH v3 4/9] rcu: Simplify rcu_init_geometry() capacity arithmetics
Current code suggests that introducing the extra level to rcu_capacity[] array makes some of the arithmetic easier. Well, in fact it appears rather confusing and unnecessary. Cc: Paul E. McKenney paul...@linux.vnet.ibm.com Cc: Steven Rostedt rost...@goodmis.org Signed-off-by: Alexander Gordeev agord...@redhat.com --- kernel/rcu/tree.c | 18 -- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 79c91d4..fb5a4cb 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4082,7 +4082,7 @@ static void __init rcu_init_geometry(void) { ulong d; int i; - int rcu_capacity[MAX_RCU_LVLS + 1]; + int rcu_capacity[MAX_RCU_LVLS]; /* * Initialize any unspecified boot parameters. @@ -4119,29 +4119,27 @@ static void __init rcu_init_geometry(void) /* * Compute number of nodes that can be handled an rcu_node tree -* with the given number of levels. Setting rcu_capacity[0] makes -* some of the arithmetic easier. +* with the given number of levels. */ - rcu_capacity[0] = 1; - rcu_capacity[1] = rcu_fanout_leaf; - for (i = 2; i = MAX_RCU_LVLS; i++) + rcu_capacity[0] = rcu_fanout_leaf; + for (i = 1; i MAX_RCU_LVLS; i++) rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT; /* * The tree must be able to accommodate the configured number of CPUs. * If this limit is exceeded than we have a serious problem elsewhere. */ - if (nr_cpu_ids rcu_capacity[MAX_RCU_LVLS]) + if (nr_cpu_ids rcu_capacity[MAX_RCU_LVLS - 1]) panic(rcu_init_geometry: rcu_capacity[] is too small); /* Calculate the number of levels in the tree. */ - for (i = 1; nr_cpu_ids rcu_capacity[i]; i++) { + for (i = 0; nr_cpu_ids rcu_capacity[i]; i++) { } - rcu_num_lvls = i; + rcu_num_lvls = i + 1; /* Calculate the number of rcu_nodes at each level of the tree. */ for (i = 0; i rcu_num_lvls; i++) { - int cap = rcu_capacity[rcu_num_lvls - i]; + int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); } -- 1.8.3.1 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/