[PATCH][RSDL-mm 4/6] sched: dont renice kernel threads

[PATCH][RSDL-mm 4/6] sched: dont renice kernel threads

[Con Kolivas]

The practice of renicing kernel threads to negative nice values is of
questionable benefit at best, and at worst leads to larger latencies when
kernel threads are busy on behalf of other tasks.

Signed-off-by: Con Kolivas <kernel@kolivas.org>

---
 kernel/workqueue.c |    1 -
 1 file changed, 1 deletion(-)

Index: linux-2.6.21-rc3-mm2/kernel/workqueue.c
===================================================================
--- linux-2.6.21-rc3-mm2.orig/kernel/workqueue.c	2007-03-16 23:27:49.000000000 +1100
+++ linux-2.6.21-rc3-mm2/kernel/workqueue.c	2007-03-16 23:27:51.000000000 +1100
@@ -294,7 +294,6 @@ static int worker_thread(void *__cwq)
 	if (!cwq->wq->freezeable)
 		current->flags |= PF_NOFREEZE;
 
-	set_user_nice(current, -5);
 	/*
 	 * We inherited MPOL_INTERLEAVE from the booting kernel.
 	 * Set MPOL_DEFAULT to insure node local allocations.

-- 
-ck

Re: [PATCH][RSDL-mm 4/6] sched: dont renice kernel threads

[Chris Friesen]

Con Kolivas wrote:
> The practice of renicing kernel threads to negative nice values is of
> questionable benefit at best, and at worst leads to larger latencies when
> kernel threads are busy on behalf of other tasks.

What about the priority implications of the renicing?  It seems a bit 
iffy letting kernel threads compete for cpu time on an equal basis with 
your default shell.

Chris

Re: [PATCH][RSDL-mm 4/6] sched: dont renice kernel threads

[Con Kolivas]

On Saturday 17 March 2007 02:14, Chris Friesen wrote:
> Con Kolivas wrote:
> > The practice of renicing kernel threads to negative nice values is of
> > questionable benefit at best, and at worst leads to larger latencies when
> > kernel threads are busy on behalf of other tasks.
>
> What about the priority implications of the renicing?  It seems a bit
> iffy letting kernel threads compete for cpu time on an equal basis with
> your default shell.

Lots of things we do because we just assume they're a good idea without any 
evidence. Renicing kernel threads was always considered a good idea on this 
basis. I'm certain noone has ever proven that it's a good thing though. 
Either way, the latest version of rsdl is robust enough that it works fine 
with reniced kernel threads if you still believe that's advantageous. This is 
definitely open for discussion/opinion.

-- 
-ck