All of lore.kernel.org
 help / color / mirror / Atom feed
From: Tianqiang Xu <skyele@sjtu.edu.cn>
To: x86@kernel.org
Cc: pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com,
	wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	kvm@vger.kernel.org, hpa@zytor.com, jarkko@kernel.org,
	dave.hansen@linux.intel.com, linux-kernel@vger.kernel.org,
	linux-sgx@vger.kernel.org, Tianqiang Xu <skyele@sjtu.edu.cn>
Subject: [PATCH 4/4] KVM guest implementation
Date: Tue, 31 Aug 2021 09:59:19 +0800	[thread overview]
Message-ID: <20210831015919.13006-4-skyele@sjtu.edu.cn> (raw)
In-Reply-To: <20210831015919.13006-1-skyele@sjtu.edu.cn>

Guest OS uses 'is_idle' field of kvm_steal_time to know if a pCPU
is idle and decides whether to schedule a task to a preempted vCPU
or not. If the pCPU is idle, scheduling a task to this pCPU will
improve cpu utilization. If not, avoiding scheduling a task to this
preempted vCPU can avoid host/guest switch, hence improving performance.

Guest OS invokes available_idle_cpu_sched() to get the value of
'is_idle' field of kvm_steal_time.

Other modules in kernel except kernel/sched/fair.c which invokes
available_idle_cpu() is left unchanged, because other modules in
kernel need the semantic provided by 'preempted' field of kvm_steal_time.

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

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

---
 kernel/sched/fair.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 44c452072a1b..f69f0a8d2abe 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5871,13 +5871,13 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
 	 * a cpufreq perspective, it's better to have higher utilisation
 	 * on one CPU.
 	 */
-	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
-		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
+	if (available_idle_cpu_sched(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
+		return available_idle_cpu_sched(prev_cpu) ? prev_cpu : this_cpu;
 
 	if (sync && cpu_rq(this_cpu)->nr_running == 1)
 		return this_cpu;
 
-	if (available_idle_cpu(prev_cpu))
+	if (available_idle_cpu_sched(prev_cpu))
 		return prev_cpu;
 
 	return nr_cpumask_bits;
@@ -5976,7 +5976,7 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this
 		if (sched_idle_cpu(i))
 			return i;
 
-		if (available_idle_cpu(i)) {
+		if (available_idle_cpu_sched(i)) {
 			struct cpuidle_state *idle = idle_get_state(rq);
 			if (idle && idle->exit_latency < min_exit_latency) {
 				/*
@@ -6064,7 +6064,7 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
 
 static inline int __select_idle_cpu(int cpu, struct task_struct *p)
 {
-	if ((available_idle_cpu(cpu) || sched_idle_cpu(cpu)) &&
+	if ((available_idle_cpu_sched(cpu) || sched_idle_cpu(cpu)) &&
 	    sched_cpu_cookie_match(cpu_rq(cpu), p))
 		return cpu;
 
@@ -6115,7 +6115,7 @@ void __update_idle_core(struct rq *rq)
 		if (cpu == core)
 			continue;
 
-		if (!available_idle_cpu(cpu))
+		if (!available_idle_cpu_sched(cpu))
 			goto unlock;
 	}
 
@@ -6138,7 +6138,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
 		return __select_idle_cpu(core, p);
 
 	for_each_cpu(cpu, cpu_smt_mask(core)) {
-		if (!available_idle_cpu(cpu)) {
+		if (!available_idle_cpu_sched(cpu)) {
 			idle = false;
 			if (*idle_cpu == -1) {
 				if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
@@ -6171,7 +6171,7 @@ static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int t
 		if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
 		    !cpumask_test_cpu(cpu, sched_domain_span(sd)))
 			continue;
-		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
+		if (available_idle_cpu_sched(cpu) || sched_idle_cpu(cpu))
 			return cpu;
 	}
 
@@ -6302,7 +6302,7 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
 	for_each_cpu_wrap(cpu, cpus, target) {
 		unsigned long cpu_cap = capacity_of(cpu);
 
-		if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
+		if (!available_idle_cpu_sched(cpu) && !sched_idle_cpu(cpu))
 			continue;
 		if (fits_capacity(task_util, cpu_cap))
 			return cpu;
@@ -6348,7 +6348,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	 */
 	lockdep_assert_irqs_disabled();
 
-	if ((available_idle_cpu(target) || sched_idle_cpu(target)) &&
+	if ((available_idle_cpu_sched(target) || sched_idle_cpu(target)) &&
 	    asym_fits_capacity(task_util, target))
 		return target;
 
@@ -6356,7 +6356,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	 * If the previous CPU is cache affine and idle, don't be stupid:
 	 */
 	if (prev != target && cpus_share_cache(prev, target) &&
-	    (available_idle_cpu(prev) || sched_idle_cpu(prev)) &&
+	    (available_idle_cpu_sched(prev) || sched_idle_cpu(prev)) &&
 	    asym_fits_capacity(task_util, prev))
 		return prev;
 
@@ -6379,7 +6379,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	if (recent_used_cpu != prev &&
 	    recent_used_cpu != target &&
 	    cpus_share_cache(recent_used_cpu, target) &&
-	    (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
+	    (available_idle_cpu_sched(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
 	    cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) &&
 	    asym_fits_capacity(task_util, recent_used_cpu)) {
 		/*
-- 
2.26.0


  parent reply	other threads:[~2021-08-31  2:01 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-31  1:59 [PATCH 1/4] KVM: x86: Introduce .pcpu_is_idle() stub infrastructure Tianqiang Xu
2021-08-31  1:59 ` [PATCH 2/4] Scheduler changes Tianqiang Xu
2021-08-31  7:14   ` Peter Zijlstra
2021-08-31  1:59 ` [PATCH 3/4] KVM host implementation Tianqiang Xu
2021-08-31  7:16   ` Peter Zijlstra
2021-08-31  7:17     ` Peter Zijlstra
2021-08-31  1:59 ` Tianqiang Xu [this message]
2021-08-31  7:21   ` [PATCH 4/4] KVM guest implementation Peter Zijlstra
2021-09-01  4:39 ` [PATCH 1/4] KVM: x86: Introduce .pcpu_is_idle() stub infrastructure Jarkko Sakkinen
2021-12-17  9:39 ` Jinrong Liang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210831015919.13006-4-skyele@sjtu.edu.cn \
    --to=skyele@sjtu.edu.cn \
    --cc=bp@alien8.de \
    --cc=dave.hansen@linux.intel.com \
    --cc=hpa@zytor.com \
    --cc=jarkko@kernel.org \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-sgx@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=seanjc@google.com \
    --cc=tglx@linutronix.de \
    --cc=vkuznets@redhat.com \
    --cc=wanpengli@tencent.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.