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From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: "'Nick Piggin'" <nickpiggin@yahoo.com.au>
Cc: "Con Kolivas" <kernel@kolivas.org>, <linux-kernel@vger.kernel.org>,
       "'Chris Mason'" <mason@suse.com>, "Ingo Molnar" <mingo@elte.hu>
Subject: RE: [PATCH RFC] smt nice introduces significant lock contention
Date: Fri, 2 Jun 2006 02:17:32 -0700
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Nick Piggin wrote on Friday, June 02, 2006 1:56 AM
> Chen, Kenneth W wrote:
> 
> > Ha, you beat me by one minute. It did cross my mind to use try lock there as
> > well, take a look at my version, I think I have a better inner loop.
> 
> Actually you *have* to use trylocks I think, because the current runqueue
> is already locked.

You are absolutely correct.  I forgot about the lock ordering.


> And why do we lock all siblings in the other case, for that matter? (not
> that it makes much difference except on niagara today).
> 
> Rolled up patch with everyone's changes attached.

What about the part in dependent_sleeper() being so bully and actively
resched other low priority sibling tasks?  I think it would be better
to just let the tasks running on sibling CPU to finish its current time
slice and then let the backoff logic to kick in.

- Ken