linux-kernel - Re: [RFC PATCH v2 11/17] sched: Basic tracking of matching tasks

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Date:   Tue, 23 Apr 2019 17:08:08 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Vineeth Remanan Pillai <vpillai@...italocean.com>,
        Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, subhra.mazumdar@...cle.com,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [RFC PATCH v2 11/17] sched: Basic tracking of matching tasks

On 4/23/19 9:18 AM, Vineeth Remanan Pillai wrote:

> +/* real prio, less is less */
> +static inline bool __prio_less(struct task_struct *a, struct task_struct *b, bool core_cmp)
> +{
> +	u64 vruntime;
> +
> +	int pa = __task_prio(a), pb = __task_prio(b);
> +
> +	if (-pa < -pb)
> +		return true;
> +
> +	if (-pb < -pa)
> +		return false;
> +
> +	if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
> +		return !dl_time_before(a->dl.deadline, b->dl.deadline);
> +
> +	vruntime = b->se.vruntime;
> +	if (core_cmp) {
> +		vruntime -= task_cfs_rq(b)->min_vruntime;
> +		vruntime += task_cfs_rq(a)->min_vruntime;
> +	}
> +	if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
> +		return !((s64)(a->se.vruntime - vruntime) <= 0);
> +
> +	return false;
> +}
> +
> +static inline bool cpu_prio_less(struct task_struct *a, struct task_struct *b)
> +{
> +	return __prio_less(a, b, false);
> +}
> +
> +static inline bool core_prio_less(struct task_struct *a, struct task_struct *b)
> +{
> +	return __prio_less(a, b, true);
> +}
> +
> +static inline bool __sched_core_less(struct task_struct *a, struct task_struct *b)
> +{
> +	if (a->core_cookie < b->core_cookie)
> +		return true;
> +
> +	if (a->core_cookie > b->core_cookie)
> +		return false;
> +
> +	/* flip prio, so high prio is leftmost */
> +	if (cpu_prio_less(b, a))
> +		return true;
> +
> +	return false;
> +}
> +

A minor nitpick.  I find keeping the vruntime base readjustment in
core_prio_less probably is more straight forward rather than pass a
core_cmp bool around.

Tim


diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 455e7ecc2f48..5917fb85669b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -100,15 +87,13 @@ static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
  */
 
 /* real prio, less is less */
-static inline bool __prio_less(struct task_struct *a, struct task_struct *b, bool core_cmp)
+static inline bool __prio_less(struct task_struct *a, struct task_struct *b, u64 vruntime)
 {
-	u64 vruntime;
-
 	int pa = __task_prio(a), pb = __task_prio(b);
 
 	trace_printk("(%s/%d;%d,%Lu,%Lu) ?< (%s/%d;%d,%Lu,%Lu)\n",
-		     a->comm, a->pid, pa, a->se.vruntime, a->dl.deadline,
-		     b->comm, b->pid, pa, b->se.vruntime, b->dl.deadline);
+			a->comm, a->pid, pa, a->se.vruntime, a->dl.deadline,
+			b->comm, b->pid, pa, b->se.vruntime, b->dl.deadline);
 
 	if (-pa < -pb)
 		return true;
@@ -119,11 +104,6 @@ static inline bool __prio_less(struct task_struct *a, struct task_struct *b, boo
 	if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
 		return !dl_time_before(a->dl.deadline, b->dl.deadline);
 
-	vruntime = b->se.vruntime;
-	if (core_cmp) {
-		vruntime -= task_cfs_rq(b)->min_vruntime;
-		vruntime += task_cfs_rq(a)->min_vruntime;
-	}
 	if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
 		return !((s64)(a->se.vruntime - vruntime) <= 0);
 
@@ -132,12 +112,17 @@ static inline bool __prio_less(struct task_struct *a, struct task_struct *b, boo
 
 static inline bool cpu_prio_less(struct task_struct *a, struct task_struct *b)
 {
-	return __prio_less(a, b, false);
+	return __prio_less(a, b, b->se.vruntime);
 }
 
 static inline bool core_prio_less(struct task_struct *a, struct task_struct *b)
 {
-	return __prio_less(a, b, true);
+	u64 vruntime = b->se.vruntime;
+
+	vruntime -= task_cfs_rq(b)->min_vruntime;
+	vruntime += task_cfs_rq(a)->min_vruntime;
+
+	return __prio_less(a, b, vruntime);
 }
 
 static inline bool __sched_core_less(struct task_struct *a, struct task_struct *b)