linux-kernel - [tip: sched/core] x86/sched/itmt: Give all SMT siblings of a core the same priority

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Date:   Wed, 10 May 2023 13:49:10 -0000
From:   "tip-bot2 for Ricardo Neri" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Len Brown <len.brown@...el.com>,
        Zhang Rui <rui.zhang@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] x86/sched/itmt: Give all SMT siblings of a core the
 same priority

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     046a5a95c3b0425cfe79e43021d8ee90c1c4f8c9
Gitweb:        https://git.kernel.org/tip/046a5a95c3b0425cfe79e43021d8ee90c1c4f8c9
Author:        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
AuthorDate:    Thu, 06 Apr 2023 13:31:47 -07:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 08 May 2023 10:58:38 +02:00

x86/sched/itmt: Give all SMT siblings of a core the same priority

X86 does not have the SD_ASYM_PACKING flag in the SMT domain. The scheduler
knows how to handle SMT and non-SMT cores of different priority. There is
no reason for SMT siblings of a core to have different priorities.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Len Brown <len.brown@...el.com>
Tested-by: Zhang Rui <rui.zhang@...el.com>
Link: https://lore.kernel.org/r/20230406203148.19182-12-ricardo.neri-calderon@linux.intel.com
---
 arch/x86/kernel/itmt.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/itmt.c b/arch/x86/kernel/itmt.c
index 670eb08..ee4fe8c 100644
--- a/arch/x86/kernel/itmt.c
+++ b/arch/x86/kernel/itmt.c
@@ -165,32 +165,19 @@ int arch_asym_cpu_priority(int cpu)
 
 /**
  * sched_set_itmt_core_prio() - Set CPU priority based on ITMT
- * @prio:	Priority of cpu core
- * @core_cpu:	The cpu number associated with the core
+ * @prio:	Priority of @cpu
+ * @cpu:	The CPU number
  *
  * The pstate driver will find out the max boost frequency
  * and call this function to set a priority proportional
- * to the max boost frequency. CPU with higher boost
+ * to the max boost frequency. CPUs with higher boost
  * frequency will receive higher priority.
  *
  * No need to rebuild sched domain after updating
  * the CPU priorities. The sched domains have no
  * dependency on CPU priorities.
  */
-void sched_set_itmt_core_prio(int prio, int core_cpu)
+void sched_set_itmt_core_prio(int prio, int cpu)
 {
-	int cpu, i = 1;
-
-	for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) {
-		int smt_prio;
-
-		/*
-		 * Ensure that the siblings are moved to the end
-		 * of the priority chain and only used when
-		 * all other high priority cpus are out of capacity.
-		 */
-		smt_prio = prio * smp_num_siblings / (i * i);
-		per_cpu(sched_core_priority, cpu) = smt_prio;
-		i++;
-	}
+	per_cpu(sched_core_priority, cpu) = prio;
 }