linux-kernel - Re: sched: Avoid SMT siblings in select_idle

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Message-ID: <1321544313.6308.25.camel@marge.simson.net>
Date:	Thu, 17 Nov 2011 16:38:33 +0100
From:	Mike Galbraith <efault@....de>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>
Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible

On Thu, 2011-11-17 at 02:59 +0100, Mike Galbraith wrote:
> On Wed, 2011-11-16 at 10:37 -0800, Suresh Siddha wrote:

> > It should be ok. Isn't it?
> 
> Nope, wasn't ok.

Because you can't get to again: with a single E5620 package, it having
only SIBLING and MC domains.
 
again:
        for_each_domain(target, sd) {
                if (!smt && (sd->flags & SD_SHARE_CPUPOWER))
                        continue;

                if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) {
                        if (!smt) {
                                smt = 1;
                                goto again;

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