linux-kernel - [PATCH 2/4] Scheduler changes

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Message-Id: <20210831015919.13006-2-skyele@sjtu.edu.cn>
Date:   Tue, 31 Aug 2021 09:59:17 +0800
From:   Tianqiang Xu <skyele@...u.edu.cn>
To:     x86@...nel.org
Cc:     pbonzini@...hat.com, seanjc@...gle.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        kvm@...r.kernel.org, hpa@...or.com, jarkko@...nel.org,
        dave.hansen@...ux.intel.com, linux-kernel@...r.kernel.org,
        linux-sgx@...r.kernel.org, Tianqiang Xu <skyele@...u.edu.cn>
Subject: [PATCH 2/4] Scheduler changes

available_idle_cpu_sched() invokes pcpu_is_idle() to detect whether
a pCPU where the preempted vCPU most recently run is idle or not, which
is used by the guest OS.

get_cpu_nr_running() gets the run queue of current cpu, which is used
by the host KVM to know whether a pCPU where the preempted vCPU mostly
recently run is idle or not.

--
Authors: Tianqiang Xu, Dingji Li, Zeyu Mi
	 Shanghai Jiao Tong University

Signed-off-by: Tianqiang Xu <skyele@...u.edu.cn>

---
 include/linux/sched.h |  1 +
 kernel/sched/core.c   | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index ec8d07d88641..dd4c41d2d8d3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1736,6 +1736,7 @@ extern int can_nice(const struct task_struct *p, const int nice);
 extern int task_curr(const struct task_struct *p);
 extern int idle_cpu(int cpu);
 extern int available_idle_cpu(int cpu);
+extern int available_idle_cpu_sched(int cpu);
 extern int sched_setscheduler(struct task_struct *, int, const struct sched_param *);
 extern int sched_setscheduler_nocheck(struct task_struct *, int, const struct sched_param *);
 extern void sched_set_fifo(struct task_struct *p);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f3b27c6c5153..c777dbcbeb9c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6752,6 +6752,17 @@ int available_idle_cpu(int cpu)
 	return 1;
 }
 
+int available_idle_cpu_sched(int cpu)
+{
+	if (!idle_cpu(cpu))
+		return 0;
+
+	if (!pcpu_is_idle(cpu))
+		return 0;
+
+	return 1;
+}
+
 /**
  * idle_task - return the idle task for a given CPU.
  * @cpu: the processor in question.
@@ -10504,3 +10515,9 @@ void call_trace_sched_update_nr_running(struct rq *rq, int count)
 {
         trace_sched_update_nr_running_tp(rq, count);
 }
+
+int get_cpu_nr_running(int cpu)
+{
+	return cpu_rq(cpu)->nr_running;
+}
+EXPORT_SYMBOL_GPL(get_cpu_nr_running);
-- 
2.26.0