[PATCH tip/core/rcu 02/12] rcu: Provide compile-time control for no-CBs CPUs
From: "Paul E. McKenney"
Currently, the only way to specify no-CBs CPUs is via the rcu_nocbs
kernel command-line parameter. This is inconvenient in some cases,
particularly for randconfig testing, so this commit adds a new
RCU_NOCB_CPU_DEFAULT kernel configuration parameter. Setting this
new parameter to zero (the default) retains the old behavior, setting
it to one offloads callback processing from CPU 0 (along with any
other CPUs specified by the rcu_nocbs boot-time parameter), and setting
it to two offloads callback processing from all CPUs.
Signed-off-by: Paul E. McKenney
Signed-off-by: Paul E. McKenney
---
init/Kconfig| 35 +++
kernel/rcutree_plugin.h | 14 ++
2 files changed, 49 insertions(+), 0 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index 97fc178..9a04156 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -686,6 +686,41 @@ config RCU_NOCB_CPU
Say Y here if you want to help to debug reduced OS jitter.
Say N here if you are unsure.
+choice
+ prompt "Build-forced no-CBs CPUs"
+ default RCU_NOCB_CPU_NONE
+
+config RCU_NOCB_CPU_NONE
+ bool "No build_forced no-CBs CPUs"
+ depends on RCU_NOCB_CPU
+ help
+ This option does not force any of the CPUs to be no-CBs CPUs.
+ Only CPUs designated by the rcu_nocbs= boot parameter will be
+ no-CBs CPUs.
+
+config RCU_NOCB_CPU_ZERO
+ bool "CPU 0 is a build_forced no-CBs CPU"
+ depends on RCU_NOCB_CPU
+ help
+ This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
+ may be designated as no-CBs CPUs using the rcu_nocbs= boot
+ parameter will be no-CBs CPUs.
+
+ Select this if CPU 0 needs to be a no-CBs CPU for real-time
+ or energy-efficiency reasons.
+
+config RCU_NOCB_CPU_ALL
+ bool "All CPUs are build_forced no-CBs CPUs"
+ depends on RCU_NOCB_CPU
+ help
+ This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
+ boot parameter will be ignored.
+
+ Select this if all CPUs need to be no-CBs CPUs for real-time
+ or energy-efficiency reasons.
+
+endchoice
+
endmenu # "RCU Subsystem"
config IKCONFIG
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 2db3160..e32236e 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -85,6 +85,20 @@ static void __init rcu_bootup_announce_oddness(void)
if (nr_cpu_ids != NR_CPUS)
printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to
nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
#ifdef CONFIG_RCU_NOCB_CPU
+#ifndef CONFIG_RCU_NOCB_CPU_NONE
+ if (!have_rcu_nocb_mask) {
+ alloc_bootmem_cpumask_var(_nocb_mask);
+ have_rcu_nocb_mask = true;
+ }
+#ifdef CONFIG_RCU_NOCB_CPU_ZERO
+ pr_info("\tExperimental no-CBs CPU 0\n");
+ cpumask_set_cpu(0, rcu_nocb_mask);
+#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */
+#ifdef CONFIG_RCU_NOCB_CPU_ALL
+ pr_info("\tExperimental no-CBs for all CPUs\n");
+ cpumask_setall(rcu_nocb_mask);
+#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */
if (have_rcu_nocb_mask) {
cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
pr_info("\tExperimental no-CBs CPUs: %s.\n", nocb_buf);
--
1.7.8
--
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[PATCH tip/core/rcu 02/12] rcu: Provide compile-time control for no-CBs CPUs
From: Paul E. McKenney paul.mcken...@linaro.org
Currently, the only way to specify no-CBs CPUs is via the rcu_nocbs
kernel command-line parameter. This is inconvenient in some cases,
particularly for randconfig testing, so this commit adds a new
RCU_NOCB_CPU_DEFAULT kernel configuration parameter. Setting this
new parameter to zero (the default) retains the old behavior, setting
it to one offloads callback processing from CPU 0 (along with any
other CPUs specified by the rcu_nocbs boot-time parameter), and setting
it to two offloads callback processing from all CPUs.
Signed-off-by: Paul E. McKenney paul.mcken...@linaro.org
Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com
---
init/Kconfig| 35 +++
kernel/rcutree_plugin.h | 14 ++
2 files changed, 49 insertions(+), 0 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index 97fc178..9a04156 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -686,6 +686,41 @@ config RCU_NOCB_CPU
Say Y here if you want to help to debug reduced OS jitter.
Say N here if you are unsure.
+choice
+ prompt Build-forced no-CBs CPUs
+ default RCU_NOCB_CPU_NONE
+
+config RCU_NOCB_CPU_NONE
+ bool No build_forced no-CBs CPUs
+ depends on RCU_NOCB_CPU
+ help
+ This option does not force any of the CPUs to be no-CBs CPUs.
+ Only CPUs designated by the rcu_nocbs= boot parameter will be
+ no-CBs CPUs.
+
+config RCU_NOCB_CPU_ZERO
+ bool CPU 0 is a build_forced no-CBs CPU
+ depends on RCU_NOCB_CPU
+ help
+ This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
+ may be designated as no-CBs CPUs using the rcu_nocbs= boot
+ parameter will be no-CBs CPUs.
+
+ Select this if CPU 0 needs to be a no-CBs CPU for real-time
+ or energy-efficiency reasons.
+
+config RCU_NOCB_CPU_ALL
+ bool All CPUs are build_forced no-CBs CPUs
+ depends on RCU_NOCB_CPU
+ help
+ This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
+ boot parameter will be ignored.
+
+ Select this if all CPUs need to be no-CBs CPUs for real-time
+ or energy-efficiency reasons.
+
+endchoice
+
endmenu # RCU Subsystem
config IKCONFIG
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 2db3160..e32236e 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -85,6 +85,20 @@ static void __init rcu_bootup_announce_oddness(void)
if (nr_cpu_ids != NR_CPUS)
printk(KERN_INFO \tRCU restricting CPUs from NR_CPUS=%d to
nr_cpu_ids=%d.\n, NR_CPUS, nr_cpu_ids);
#ifdef CONFIG_RCU_NOCB_CPU
+#ifndef CONFIG_RCU_NOCB_CPU_NONE
+ if (!have_rcu_nocb_mask) {
+ alloc_bootmem_cpumask_var(rcu_nocb_mask);
+ have_rcu_nocb_mask = true;
+ }
+#ifdef CONFIG_RCU_NOCB_CPU_ZERO
+ pr_info(\tExperimental no-CBs CPU 0\n);
+ cpumask_set_cpu(0, rcu_nocb_mask);
+#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */
+#ifdef CONFIG_RCU_NOCB_CPU_ALL
+ pr_info(\tExperimental no-CBs for all CPUs\n);
+ cpumask_setall(rcu_nocb_mask);
+#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */
+#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */
if (have_rcu_nocb_mask) {
cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask);
pr_info(\tExperimental no-CBs CPUs: %s.\n, nocb_buf);
--
1.7.8
--
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