The patch titled
Subject: kernel/sys.c: migrate shutdown/reboot to boot cpu.
has been added to the -mm tree. Its filename is
kernel-sysc-migrate-shutdown-reboot-to-boot-cpu.patch
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------------------------------------------------------
From: Robin Holt <holt@xxxxxxx>
Subject: kernel/sys.c: migrate shutdown/reboot to boot cpu.
We recently noticed that reboot of a 1024 cpu machine takes approx 16
minutes of just stopping the cpus. The slowdown was tracked to commit
f96972f ("kernel/sys.c: call disable_nonboot_cpus() in kernel_restart()").
The current implementation does all the work of hot removing the cpus
before halting the system. We are switching to just migrating to the boot
cpu and then continuing with shutdown/reboot.
This also has the effect of not breaking x86's command line parameter for
specifying the reboot cpu. Note, this code was shamelessly copied from
arch/x86/kernel/reboot.c with bits removed pertaining to the reboot_cpu
command line parameter.
Signed-off-by: Robin Holt <holt@xxxxxxx>
Tested-by: Shawn Guo <shawn.guo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Robin Holt <holt@xxxxxxx>
Cc: Russ Anderson <rja@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sys.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
diff -puN kernel/sys.c~kernel-sysc-migrate-shutdown-reboot-to-boot-cpu kernel/sys.c
--- a/kernel/sys.c~kernel-sysc-migrate-shutdown-reboot-to-boot-cpu
+++ a/kernel/sys.c
@@ -362,6 +362,24 @@ int unregister_reboot_notifier(struct no
}
EXPORT_SYMBOL(unregister_reboot_notifier);
+static void migrate_to_reboot_cpu(void)
+{
+ /* The boot cpu is always logical cpu 0 */
+ int reboot_cpu_id = 0;
+
+ cpu_hotplug_disable();
+
+ /* Make certain the cpu I'm about to reboot on is online */
+ if (!cpu_online(reboot_cpu_id))
+ reboot_cpu_id = cpumask_first(cpu_online_mask);
+
+ /* Prevent races with other tasks migrating this task */
+ current->flags |= PF_THREAD_BOUND;
+
+ /* Make certain I only run on the appropriate processor */
+ set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id));
+}
+
/**
* kernel_restart - reboot the system
* @cmd: pointer to buffer containing command to execute for restart
@@ -373,7 +391,7 @@ EXPORT_SYMBOL(unregister_reboot_notifier
void kernel_restart(char *cmd)
{
kernel_restart_prepare(cmd);
- disable_nonboot_cpus();
+ migrate_to_reboot_cpu();
syscore_shutdown();
if (!cmd)
printk(KERN_EMERG "Restarting system.\n");
@@ -400,7 +418,7 @@ static void kernel_shutdown_prepare(enum
void kernel_halt(void)
{
kernel_shutdown_prepare(SYSTEM_HALT);
- disable_nonboot_cpus();
+ migrate_to_reboot_cpu();
syscore_shutdown();
printk(KERN_EMERG "System halted.\n");
kmsg_dump(KMSG_DUMP_HALT);
@@ -419,7 +437,7 @@ void kernel_power_off(void)
kernel_shutdown_prepare(SYSTEM_POWER_OFF);
if (pm_power_off_prepare)
pm_power_off_prepare();
- disable_nonboot_cpus();
+ migrate_to_reboot_cpu();
syscore_shutdown();
printk(KERN_EMERG "Power down.\n");
kmsg_dump(KMSG_DUMP_POWEROFF);
_
Patches currently in -mm which might be from holt@xxxxxxx are
cpu-hotplug-provide-a-generic-helper-to-disable-enable-cpu-hotplug.patch
kernel-sysc-migrate-shutdown-reboot-to-boot-cpu.patch
kernel-sysc-move-shutdown-reboot-related-functions-to-kernel-rebootc.patch
kernel-rebootc-fix-checkpatch-warnings.patch
kernel-rebootc-move-arch-x86-reboot=-handling-to-generic-kernel.patch
ipc-sysv-shared-memory-limited-to-8tib.patch
ipc-sysv-shared-memory-limited-to-8tib-fix.patch
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