lkml.org 
[lkml]   [2001]   [Jul]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: CPU affinity & IPI latency

On 13-Jul-2001 Mike Kravetz wrote:
> On Fri, Jul 13, 2001 at 09:41:44AM -0700, Davide Libenzi wrote:
>>
>> I personally think that a standard scheduler/cpu is the way to go for SMP.
>> I saw the one IBM guys did and I think that the wrong catch there is trying
>> always to grab the best task to run over all CPUs.
>
> That was me/us. Most of the reason for making 'global scheduling'
> decisions was an attempt to maintain the same behavior as the existing
> scheduler. We are trying to see how well we can make this scheduler
> scale, while maintaining this global behavior. Thought is that if
> there was ever any hope of someone adopting this scheduler, they would
> be more likely to do so if it attempted to maintain existing behavior.

The problem, IMHO, is that we're trying to extend what is a correct behaviour on
the UP scheduler ( pickup the best task to run ) to SMP machines.
Global scheduling decisions should be triggered in response of load unbalancing
and not at each schedule() run otherwise we're going to introduce a common lock
that will limit the overall scalability.
My idea about the future of the scheduler is to have a config options users can
chose depending upon the machine use.
By trying to keep a unique scheduler for both UP and MP is like going to give
the same answer to different problems and the scaling factor ( of the scheduler
itself ) on SMP will never improve.
The code inside kernel/sched.c should be reorganized ( it contains even not
scheduler code ) so that the various CONFIG_SCHED* will not introduce any messy
inside the code ( possibly by having the code in separate files
kernel/sched*.c ).




- Davide

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:57    [W:0.060 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site