linux-kernel - [RFC][PATCH 4/6] sched: eliminate "DIE" domain level when NUMA present

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Message-Id: <20140917223316.FCEAF8FB@viggo.jf.intel.com>
Date:	Wed, 17 Sep 2014 15:33:16 -0700
From:	Dave Hansen <dave@...1.net>
To:	a.p.zijlstra@...llo.nl
Cc:	mingo@...nel.org, hpa@...ux.intel.com, brice.goglin@...il.com,
	bp@...en8.de, linux-kernel@...r.kernel.org,
	Dave Hansen <dave@...1.net>, dave.hansen@...ux.intel.com
Subject: [RFC][PATCH 4/6] sched: eliminate "DIE" domain level when NUMA present


From: Dave Hansen <dave.hansen@...ux.intel.com>

The "DIE" topology level is currently defined like this:

static inline const struct cpumask *cpu_cpu_mask(int cpu)
{
        return cpumask_of_node(cpu_to_node(cpu));
}

But that makes very little sense on a NUMA system since
the lowest-domain NUMA node is guaranteed to be essentially
the same as this level.

We leave this for systems that are !CONFIG_NUMA and that
might need a top-level domain.

This also keeps us from having screwy topologies when the
smallest NUMA node is only _part_ of the die.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/kernel/sched/core.c |    2 ++
 1 file changed, 2 insertions(+)

diff -puN kernel/sched/core.c~die-is-NUMA-based-and-screwed-up kernel/sched/core.c
--- a/kernel/sched/core.c~die-is-NUMA-based-and-screwed-up	2014-09-17 15:28:57.867588315 -0700
+++ b/kernel/sched/core.c	2014-09-17 15:28:57.873588591 -0700
@@ -6141,7 +6141,9 @@ static struct sched_domain_topology_leve
 #ifdef CONFIG_SCHED_MC
 	{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
 #endif
+#ifndef CONFIG_NUMA
 	{ cpu_cpu_mask, SD_INIT_NAME(DIE) },
+#endif
 	{ NULL, },
 };
 
_
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