linux-kernel - Re: [patch v3 5/6] sched, ttwu_queue: queue remote wakeups only when crossing cache domains

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Message-ID: <1323336544.17673.3.camel@twins>
Date:	Thu, 08 Dec 2011 10:29:04 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Mike Galbraith <efault@....de>, Ingo Molnar <mingo@...e.hu>,
	Venki Pallipadi <venki@...gle.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Tim Chen <tim.c.chen@...ux.jf.intel.com>,
	"Shi, Alex" <alex.shi@...el.com>
Subject: Re: [patch v3 5/6] sched, ttwu_queue: queue remote wakeups only
 when crossing cache domains

On Wed, 2011-12-07 at 11:20 -0800, Suresh Siddha wrote:

> > +DEFINE_PER_CPU(int, sd_top_spr_id);
> 
> pkg_srid (shared resource id)?

How about sd_llc{,_id} ?

> > +
> > +static void update_top_cache_domain(int cpu)
> > +{
> > +	struct sched_domain *sd;
> > +	int id = -1;
> > +
> > +	sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES);
> > +	if (sd)
> > +		id = cpumask_first(sched_domain_span(sd));
> 
> if there is no sd with shared pkg resources, then id has to be set to
> 'cpu'.

Ah, right. I hadn't considered the case where the LLC isn't shared at
all.

> > +	rcu_assign_pointer(per_cpu(sd_top_spr, cpu), sd);
> > +	per_cpu(sd_top_spr_id, cpu) = id;
> 
> Otherwise it looks good.

Thanks!
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