linux-kernel - [PATCH v2 1/2] sched: Add a new function to compare if two cpus have the same capacity

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Date: Fri, 23 Feb 2024 15:57:48 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Jens Axboe <axboe@...nel.dk>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Cc: linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org,
	Sudeep Holla <sudeep.holla@....com>,
	Wei Wang <wvw@...gle.com>,
	Jaegeuk Kim <jaegeuk@...nel.org>,
	Bart Van Assche <bvanassche@....org>,
	Christoph Hellwig <hch@...radead.org>,
	Qais Yousef <qyousef@...alina.io>
Subject: [PATCH v2 1/2] sched: Add a new function to compare if two cpus have the same capacity

The new helper function is needed to help blk-mq check if it needs to
dispatch the softirq on another CPU to match the performance level the
IO requester is running at. This is important on HMP systems where not
all CPUs have the same compute capacity.

Signed-off-by: Qais Yousef <qyousef@...alina.io>
---
 include/linux/sched/topology.h |  6 ++++++
 kernel/sched/core.c            | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index a6e04b4a21d7..11e0e00e0bb9 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -176,6 +176,7 @@ extern void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
 cpumask_var_t *alloc_sched_domains(unsigned int ndoms);
 void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms);
 
+bool cpus_equal_capacity(int this_cpu, int that_cpu);
 bool cpus_share_cache(int this_cpu, int that_cpu);
 bool cpus_share_resources(int this_cpu, int that_cpu);
 
@@ -226,6 +227,11 @@ partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
 {
 }
 
+static inline bool cpus_equal_capacity(int this_cpu, int that_cpu)
+{
+	return true;
+}
+
 static inline bool cpus_share_cache(int this_cpu, int that_cpu)
 {
 	return true;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a76c7095f736..adbaabb23fa1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3953,6 +3953,17 @@ void wake_up_if_idle(int cpu)
 	}
 }
 
+bool cpus_equal_capacity(int this_cpu, int that_cpu)
+{
+	if (!sched_asym_cpucap_active())
+		return true;
+
+	if (this_cpu == that_cpu)
+		return true;
+
+	return arch_scale_cpu_capacity(this_cpu) == arch_scale_cpu_capacity(that_cpu);
+}
+
 bool cpus_share_cache(int this_cpu, int that_cpu)
 {
 	if (this_cpu == that_cpu)
-- 
2.34.1