linux-kernel - [PATCH 4.18 125/168] sched/topology: Set correct NUMA topology type

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Message-Id: <20181008175624.800138207@linuxfoundation.org>
Date:   Mon,  8 Oct 2018 20:31:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Andre Wild <wild@...ux.vnet.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Rik van Riel <riel@...riel.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Ingo Molnar <mingo@...nel.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.18 125/168] sched/topology: Set correct NUMA topology type

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

[ Upstream commit e5e96fafd9028b1478b165db78c52d981c14f471 ]

With the following commit:

  051f3ca02e46 ("sched/topology: Introduce NUMA identity node sched domain")

the scheduler introduced a new NUMA level. However this leads to the NUMA topology
on 2 node systems to not be marked as NUMA_DIRECT anymore.

After this commit, it gets reported as NUMA_BACKPLANE, because
sched_domains_numa_level is now 2 on 2 node systems.

Fix this by allowing setting systems that have up to 2 NUMA levels as
NUMA_DIRECT.

While here remove code that assumes that level can be 0.

Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Andre Wild <wild@...ux.vnet.ibm.com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...riel.com>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Fixes: 051f3ca02e46 "Introduce NUMA identity node sched domain"
Link: http://lkml.kernel.org/r/1533920419-17410-1-git-send-email-srikar@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/sched/topology.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1295,7 +1295,7 @@ static void init_numa_topology_type(void
 
 	n = sched_max_numa_distance;
 
-	if (sched_domains_numa_levels <= 1) {
+	if (sched_domains_numa_levels <= 2) {
 		sched_numa_topology_type = NUMA_DIRECT;
 		return;
 	}
@@ -1380,9 +1380,6 @@ void sched_init_numa(void)
 			break;
 	}
 
-	if (!level)
-		return;
-
 	/*
 	 * 'level' contains the number of unique distances
 	 *