2013-09-27 16:47:43

by Abbas Raza

Subject: [PATCH] kthread_bind: don't wait in kthread_bind for presmp initcalls

From: Abbas Raza <[email protected]>

wait_task_inactive shouldn't be called in __kthread_bind for presmp
initcalls the same way it is done in !SMP case.

more info here:
http://permalink.gmane.org/gmane.linux.kernel.embedded/4046

This patch improves boot time for pre-smp initcalls as given below

boot time with this patch:

calling spawn_ksoftirqd+0x0/0x30 @ 1
initcall spawn_ksoftirqd+0x0/0x30 returned 0 after 0 usecs

boot time without this patch:

calling spawn_ksoftirqd+0x0/0x30 @ 1
initcall spawn_ksoftirqd+0x0/0x30 returned 0 after 19531 usecs

Signed-off-by: Abbas Raza <[email protected]>
---
kernel/kthread.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 760e86d..28b5c4b 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -290,11 +290,17 @@ EXPORT_SYMBOL(kthread_create_on_node);

static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
{
- /* Must have done schedule() in kthread() before we set_task_cpu */
- if (!wait_task_inactive(p, state)) {
- WARN_ON(1);
- return;
+ if (!((num_online_cpus() == 1) && !cpu)) {
+ /*
+ * Must have done schedule() in kthread() before
+ * we set_task_cpu
+ */
+ if (!wait_task_inactive(p, state)) {
+ WARN_ON(1);
+ return;
+ }
}
+
/* It's safe because the task is inactive. */
do_set_cpus_allowed(p, cpumask_of(cpu));
p->flags |= PF_NO_SETAFFINITY;
--
1.8.3.2

2013-10-30 16:00:39

by Abbas Raza

Subject: Re: [PATCH] kthread_bind: don't wait in kthread_bind for presmp initcalls

Hi,

Any thoughts here please?

Thanks .
Abbas Raza

On 09/27/2013 09:47 PM, Abbas Raza wrote:
> From: Abbas Raza <[email protected]>
>
> wait_task_inactive shouldn't be called in __kthread_bind for presmp
> initcalls the same way it is done in !SMP case.
>
> more info here:
> http://permalink.gmane.org/gmane.linux.kernel.embedded/4046
>
> This patch improves boot time for pre-smp initcalls as given below
>
> boot time with this patch:
>
> calling spawn_ksoftirqd+0x0/0x30 @ 1
> initcall spawn_ksoftirqd+0x0/0x30 returned 0 after 0 usecs
>
> boot time without this patch:
>
> calling spawn_ksoftirqd+0x0/0x30 @ 1
> initcall spawn_ksoftirqd+0x0/0x30 returned 0 after 19531 usecs
>
> Signed-off-by: Abbas Raza <[email protected]>
> ---
> kernel/kthread.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index 760e86d..28b5c4b 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -290,11 +290,17 @@ EXPORT_SYMBOL(kthread_create_on_node);
>
> static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
> {
> - /* Must have done schedule() in kthread() before we set_task_cpu */
> - if (!wait_task_inactive(p, state)) {
> - WARN_ON(1);
> - return;
> + if (!((num_online_cpus() == 1) && !cpu)) {
> + /*
> + * Must have done schedule() in kthread() before
> + * we set_task_cpu
> + */
> + if (!wait_task_inactive(p, state)) {
> + WARN_ON(1);
> + return;
> + }
> }
> +
> /* It's safe because the task is inactive. */
> do_set_cpus_allowed(p, cpumask_of(cpu));
> p->flags |= PF_NO_SETAFFINITY;