Increase priority of a workqueue thread ?

Increase priority of a workqueue thread ?

[Block Device]

Hi,
    I am using a custom workqueue thread in my module. How do I increase the
priority of the workqueue threads ?
I've seen that each workqueue contains an array of per-cpu structures
which has a
task_struct of the thread on a particular cpu. Since these threads are
created from keventd
I think they'll have the same priority as keventd.  Also the per-cpu
structure is something which is private to the workqueue
implementation. Directly using it (from my driver) to increase the
priority of the workqueue doesnt seem correct to me. Is there any
interface or standard way of changing the priority of a workqueue.

Thanks
BD

Re: Increase priority of a workqueue thread ?

[linux-os (Dick Johnson)]

On Thu, 20 Oct 2005, Block Device wrote:

> Hi,
>    I am using a custom workqueue thread in my module. How do I increase the
> priority of the workqueue threads ?
> I've seen that each workqueue contains an array of per-cpu structures
> which has a
> task_struct of the thread on a particular cpu. Since these threads are
> created from keventd
> I think they'll have the same priority as keventd.  Also the per-cpu
> structure is something which is private to the workqueue
> implementation. Directly using it (from my driver) to increase the
> priority of the workqueue doesnt seem correct to me. Is there any
> interface or standard way of changing the priority of a workqueue.
>
> Thanks
> BD

I don't think you want to increase the priority of keventd.
You need to create a seperate kernel thread for your module's
work. That thread's priority can be set with set_user_nice()...

 	set_user_nice(current, -19);

Older kernels required:

 	task_lock(current);
         current->nice = -19;
         task_unlock(current);

The kernel thread can set this up when it is first started.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.
.

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Thank you.

Re: Increase priority of a workqueue thread ?

[Con Kolivas]

[-- Attachment #1: Type: text/plain, Size: 866 bytes --]

On Thu, 20 Oct 2005 23:12, Block Device wrote:
> Hi,
>     I am using a custom workqueue thread in my module. How do I increase
> the priority of the workqueue threads ?
> I've seen that each workqueue contains an array of per-cpu structures
> which has a
> task_struct of the thread on a particular cpu. Since these threads are
> created from keventd
> I think they'll have the same priority as keventd.  Also the per-cpu
> structure is something which is private to the workqueue
> implementation. Directly using it (from my driver) to increase the
> priority of the workqueue doesnt seem correct to me. Is there any
> interface or standard way of changing the priority of a workqueue.

By strange coincidence I was working on a patch to do this. Here's what I have 
so far - I know the code is safe but I don't know if it does as advertised  
yet ;)

Cheers,
Con

[-- Attachment #2: set_workqueue_nice.patch --]
[-- Type: text/x-diff, Size: 1643 bytes --]

Index: linux-2.6.14-rc4-ck1/include/linux/workqueue.h
===================================================================
--- linux-2.6.14-rc4-ck1.orig/include/linux/workqueue.h	2005-06-18 23:59:46.000000000 +1000
+++ linux-2.6.14-rc4-ck1/include/linux/workqueue.h	2005-10-11 16:03:09.000000000 +1000
@@ -56,6 +56,7 @@ extern struct workqueue_struct *__create
 #define create_singlethread_workqueue(name) __create_workqueue((name), 1)
 
 extern void destroy_workqueue(struct workqueue_struct *wq);
+extern void set_workqueue_nice(struct workqueue_struct *wq, long nice);
 
 extern int FASTCALL(queue_work(struct workqueue_struct *wq, struct work_struct *work));
 extern int FASTCALL(queue_delayed_work(struct workqueue_struct *wq, struct work_struct *work, unsigned long delay));
Index: linux-2.6.14-rc4-ck1/kernel/workqueue.c
===================================================================
--- linux-2.6.14-rc4-ck1.orig/kernel/workqueue.c	2005-10-11 15:56:13.000000000 +1000
+++ linux-2.6.14-rc4-ck1/kernel/workqueue.c	2005-10-11 16:03:09.000000000 +1000
@@ -383,6 +383,26 @@ void destroy_workqueue(struct workqueue_
 	kfree(wq);
 }
 
+void set_workqueue_nice(struct workqueue_struct *wq, long nice)
+{
+	struct task_struct *p;
+	int cpu;
+
+	lock_cpu_hotplug();
+	if (is_single_threaded(wq)) {
+		p = wq->cpu_wq->thread;
+		set_user_nice(p, nice);
+	} else {
+		for_each_online_cpu(cpu) {
+			struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
+	
+			p = cwq->thread;
+			set_user_nice(p, nice);
+		}
+	}
+	unlock_cpu_hotplug();
+}
+
 static struct workqueue_struct *keventd_wq;
 
 int fastcall schedule_work(struct work_struct *work)

Re: Increase priority of a workqueue thread ?

[Block Device]

Con, Dick,

    Thanks a lot :) ... I'll try it out and see whether it works for me :)

Regards
BD.

On 10/20/05, Con Kolivas <kernel@kolivas.org> wrote:
> On Thu, 20 Oct 2005 23:12, Block Device wrote:
> > Hi,
> >     I am using a custom workqueue thread in my module. How do I increase
> > the priority of the workqueue threads ?
> > I've seen that each workqueue contains an array of per-cpu structures
> > which has a
> > task_struct of the thread on a particular cpu. Since these threads are
> > created from keventd
> > I think they'll have the same priority as keventd.  Also the per-cpu
> > structure is something which is private to the workqueue
> > implementation. Directly using it (from my driver) to increase the
> > priority of the workqueue doesnt seem correct to me. Is there any
> > interface or standard way of changing the priority of a workqueue.
>
> By strange coincidence I was working on a patch to do this. Here's what I have
> so far - I know the code is safe but I don't know if it does as advertised
> yet ;)
>
> Cheers,
> Con
>
>
>