Motivation of doing this is to better improve boot times for devices when
we want to prevent our workqueue works from running on some specific CPUs,
i,e, some CPUs are busy with interrupts.

Also remove HK_FLAG_WQ from nohz_full to prevent nohz_full overriding
workqueue's cpu config.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: tiozhang <tiozhang@didiglobal.com>
---
 kernel/sched/isolation.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 373d42c707bc..5cd67c51622e 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -181,8 +181,8 @@ static int __init housekeeping_nohz_full_setup(char *str)
 {
 	unsigned long flags;
 
-	flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU |
-		HK_FLAG_MISC | HK_FLAG_KTHREAD;
+	flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC
+		| HK_FLAG_KTHREAD;
 
 	return housekeeping_setup(str, flags);
 }
@@ -208,6 +208,12 @@ static int __init housekeeping_isolcpus_setup(char *str)
 			continue;
 		}
 
+		if (!strncmp(str, "workqueue,", 10)) {
+			str += 10;
+			flags |= HK_FLAG_WQ;
+			continue;
+		}
+
 		if (!strncmp(str, "managed_irq,", 12)) {
 			str += 12;
 			flags |= HK_FLAG_MANAGED_IRQ;
-- 
2.17.1

On Thu, Jun 22, 2023 at 11:22:17AM +0800, tiozhang wrote:
> Motivation of doing this is to better improve boot times for devices when
> we want to prevent our workqueue works from running on some specific CPUs,
> i,e, some CPUs are busy with interrupts.
> 
> Also remove HK_FLAG_WQ from nohz_full to prevent nohz_full overriding
> workqueue's cpu config.

But then nohz_full= doesn't re-affine workqueues anymore, right?

> 
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: tiozhang <tiozhang@didiglobal.com>
> ---
>  kernel/sched/isolation.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index 373d42c707bc..5cd67c51622e 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -181,8 +181,8 @@ static int __init housekeeping_nohz_full_setup(char *str)
>  {
>  	unsigned long flags;
>  
> -	flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU |
> -		HK_FLAG_MISC | HK_FLAG_KTHREAD;
> +	flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC
> +		| HK_FLAG_KTHREAD;
>  
>  	return housekeeping_setup(str, flags);
>  }
> @@ -208,6 +208,12 @@ static int __init housekeeping_isolcpus_setup(char *str)
>  			continue;
>  		}
>  
> +		if (!strncmp(str, "workqueue,", 10)) {
> +			str += 10;
> +			flags |= HK_FLAG_WQ;
> +			continue;
> +		}
> +

I'm planning on removing HK_FLAG_TICK, HK_FLAG_WQ, HK_FLAG_TIMER, HK_FLAG_RCU,
HK_FLAG_MISC and HK_FLAG_KTHREAD and merge them all together. Also the problem with
these flags is that once they are modified on boot, you can't modify them later.

I much prefer what was done in this patch:

  https://lore.kernel.org/all/20230623073033.GA6584@didi-ThinkCentre-M930t-N000/

Thanks!

>  		if (!strncmp(str, "managed_irq,", 12)) {
>  			str += 12;
>  			flags |= HK_FLAG_MANAGED_IRQ;
> -- 
> 2.17.1
>

On Thu, Jun 22, 2023 at 11:22:17AM +0800, tiozhang wrote:
> Motivation of doing this is to better improve boot times for devices when
> we want to prevent our workqueue works from running on some specific CPUs,
> i,e, some CPUs are busy with interrupts.
> 
> Also remove HK_FLAG_WQ from nohz_full to prevent nohz_full overriding
> workqueue's cpu config.
> 
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: tiozhang <tiozhang@didiglobal.com>

Let's just do the workqueue specific parameter. I'll apply the other one to
the workqueue branch after the merge window.

Thanks.

-- 
tejun