linux-kernel - [PATCH 1/6] sched/topology: Propagate SMT flags when removing degenerate domain

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Date:   Thu,  4 May 2023 09:09:51 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Tim C Chen <tim.c.chen@...ux.intel.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V . Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Valentin Schneider <vschneid@...hat.com>,
        Ionela Voinescu <ionela.voinescu@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        naveen.n.rao@...ux.vnet.ibm.com,
        Yicong Yang <yangyicong@...ilicon.com>,
        Barry Song <v-songbaohua@...o.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: [PATCH 1/6] sched/topology: Propagate SMT flags when removing degenerate domain

From: Tim C Chen <tim.c.chen@...ux.intel.com>

When a degenerate cluster domain for core with SMT CPUs is removed,
the SD_SHARE_CPUCAPACITY flag in the local child sched group was not
propagated to the new parent.  We need this flag to properly determine
whether the local sched group is SMT.  Set the flag in the local
child sched group of the new parent sched domain.

Reviewed-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 kernel/sched/topology.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 051aaf65c749..6d5628fcebcf 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -719,8 +719,13 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
 
 		if (sd_parent_degenerate(tmp, parent)) {
 			tmp->parent = parent->parent;
-			if (parent->parent)
+
+			if (parent->parent) {
 				parent->parent->child = tmp;
+				if (tmp->flags & SD_SHARE_CPUCAPACITY)
+					parent->parent->groups->flags |= SD_SHARE_CPUCAPACITY;
+			}
+
 			/*
 			 * Transfer SD_PREFER_SIBLING down in case of a
 			 * degenerate parent; the spans match for this
-- 
2.32.0