cpumask: simplify sched_rt.c

PATCH In review Rusty Russell 3 participants 5 messages Nov 3, 2009 – Nov 4, 2009

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Rusty Russell

author

2009-11-03 04:23 UTC #0 lore raw

PATCH 1/14 cpumask: simplify sched_rt.c

find_lowest_rq() wants to call pick_optimal_cpu() on the intersection of sched_domain_span(sd) and lowest_mask. Rather than doing a cpus_and into a temporary, we can open-code it.

This actually makes the code slightly clearer, IMHO.

Signed-off-by Rusty Russell <[email protected]>

To: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>

---
 kernel/sched_rt.c |   59 +++++++++++++++++++++---------------------------------
 1 file changed, 23 insertions(+), 36 deletions(-)

kernel/sched_rt.c +23 ~~-36~~

@@ -1115,29 +1115,12 @@ static struct task_struct *pick_next_hig
 
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
 
-static inline int pick_optimal_cpu(int this_cpu,
-				   const struct cpumask *mask)
-{
-	int first;
-
-	/* "this_cpu" is cheaper to preempt than a remote processor */
-	if ((this_cpu != -1) && cpumask_test_cpu(this_cpu, mask))
-		return this_cpu;
-
-	first = cpumask_first(mask);
-	if (first < nr_cpu_ids)
-		return first;
-
-	return -1;
-}
-
 static int find_lowest_rq(struct task_struct *task)
 {
 	struct sched_domain *sd;
 	struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
 	int this_cpu = smp_processor_id();
 	int cpu      = task_cpu(task);
-	cpumask_var_t domain_mask;
 
 	if (task->rt.nr_cpus_allowed == 1)
 		return -1; /* No other targets possible */

@@ -1167,28 +1150,26 @@ static int find_lowest_rq(struct task_st
 	 * Otherwise, we consult the sched_domains span maps to figure
 	 * out which cpu is logically closest to our hot cache data.
 	 */
-	if (this_cpu == cpu)
-		this_cpu = -1; /* Skip this_cpu opt if the same */
+	if (!cpumask_test_cpu(this_cpu, lowest_mask))
+		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
 
-	if (alloc_cpumask_var(&domain_mask, GFP_ATOMIC)) {
-		for_each_domain(cpu, sd) {
-			if (sd->flags & SD_WAKE_AFFINE) {
-				int best_cpu;
+	for_each_domain(cpu, sd) {
+		if (sd->flags & SD_WAKE_AFFINE) {
+			int best_cpu;
 
-				cpumask_and(domain_mask,
-					    sched_domain_span(sd),
-					    lowest_mask);
+			/*
+			 * "this_cpu" is cheaper to preempt than a
+			 * remote processor.
+			 */
+			if (this_cpu != -1 &&
+			    cpumask_test_cpu(this_cpu, sched_domain_span(sd)))
+				return this_cpu;
 
-				best_cpu = pick_optimal_cpu(this_cpu,
-							    domain_mask);
-
-				if (best_cpu != -1) {
-					free_cpumask_var(domain_mask);
-					return best_cpu;
-				}
-			}
+			best_cpu = cpumask_first_and(lowest_mask,
+						     sched_domain_span(sd));
+			if (best_cpu < nr_cpu_ids)
+				return best_cpu;
 		}
-		free_cpumask_var(domain_mask);
 	}
 
 	/*

@@ -1196,7 +1177,13 @@ static int find_lowest_rq(struct task_st
 	 * just give the caller *something* to work with from the compatible
 	 * locations.
 	 */
-	return pick_optimal_cpu(this_cpu, lowest_mask);
+	if (this_cpu != -1)
+		return this_cpu;
+
+	cpu = cpumask_any(lowest_mask);
+	if (cpu < nr_cpu_ids)
+		return cpu;
+	return -1;
 }
 
 /* Will lock the rq it finds */

Steven Rostedt

2009-11-03 16:41 UTC #1 lore raw

Greg,

I believe this was mostly your code. Can you review this change.

Thanks,

-- Steve

Quoted 107 lines · Rusty Russell

find_lowest_rq() wants to call pick_optimal_cpu() on the intersection of sched_domain_span(sd) and lowest_mask. Rather than doing a cpus_and into a temporary, we can open-code it.

This actually makes the code slightly clearer, IMHO.

Signed-off-by Rusty Russell <[email protected]>

To: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>

---
 kernel/sched_rt.c |   59 +++++++++++++++++++++---------------------------------
 1 file changed, 23 insertions(+), 36 deletions(-)

kernel/sched_rt.c +23 ~~-36~~

@@ -1115,29 +1115,12 @@ static struct task_struct *pick_next_hig
 
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
 
-static inline int pick_optimal_cpu(int this_cpu,
-				   const struct cpumask *mask)
-{
-	int first;
-
-	/* "this_cpu" is cheaper to preempt than a remote processor */
-	if ((this_cpu != -1) && cpumask_test_cpu(this_cpu, mask))
-		return this_cpu;
-
-	first = cpumask_first(mask);
-	if (first < nr_cpu_ids)
-		return first;
-
-	return -1;
-}
-
 static int find_lowest_rq(struct task_struct *task)
 {
 	struct sched_domain *sd;
 	struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
 	int this_cpu = smp_processor_id();
 	int cpu      = task_cpu(task);
-	cpumask_var_t domain_mask;
 
 	if (task->rt.nr_cpus_allowed == 1)
 		return -1; /* No other targets possible */

@@ -1167,28 +1150,26 @@ static int find_lowest_rq(struct task_st
 	 * Otherwise, we consult the sched_domains span maps to figure
 	 * out which cpu is logically closest to our hot cache data.
 	 */
-	if (this_cpu == cpu)
-		this_cpu = -1; /* Skip this_cpu opt if the same */
+	if (!cpumask_test_cpu(this_cpu, lowest_mask))
+		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
 
-	if (alloc_cpumask_var(&domain_mask, GFP_ATOMIC)) {
-		for_each_domain(cpu, sd) {
-			if (sd->flags & SD_WAKE_AFFINE) {
-				int best_cpu;
+	for_each_domain(cpu, sd) {
+		if (sd->flags & SD_WAKE_AFFINE) {
+			int best_cpu;
 
-				cpumask_and(domain_mask,
-					    sched_domain_span(sd),
-					    lowest_mask);
+			/*
+			 * "this_cpu" is cheaper to preempt than a
+			 * remote processor.
+			 */
+			if (this_cpu != -1 &&
+			    cpumask_test_cpu(this_cpu, sched_domain_span(sd)))
+				return this_cpu;
 
-				best_cpu = pick_optimal_cpu(this_cpu,
-							    domain_mask);
-
-				if (best_cpu != -1) {
-					free_cpumask_var(domain_mask);
-					return best_cpu;
-				}
-			}
+			best_cpu = cpumask_first_and(lowest_mask,
+						     sched_domain_span(sd));
+			if (best_cpu < nr_cpu_ids)
+				return best_cpu;
 		}
-		free_cpumask_var(domain_mask);
 	}
 
 	/*

@@ -1196,7 +1177,13 @@ static int find_lowest_rq(struct task_st
 	 * just give the caller *something* to work with from the compatible
 	 * locations.
 	 */
-	return pick_optimal_cpu(this_cpu, lowest_mask);
+	if (this_cpu != -1)
+		return this_cpu;
+
+	cpu = cpumask_any(lowest_mask);
+	if (cpu < nr_cpu_ids)
+		return cpu;
+	return -1;
 }
 
 /* Will lock the rq it finds */

Gregory Haskins

2009-11-03 21:22 UTC #2 lore raw

Quoted 1 line

Quoted 1 line
Quoted 1 line
On 11/3/2009 at 11:41 AM, in message

<[email protected]>, Steven Rostedt

Quoted 4 lines · <[email protected]> wrote:

Greg,
I believe this was mostly your code. Can you review this change.

Hi Steve,
FYI: Looking now. The diff hunk layout is a little confusing, so I need to think about it a little longer.

Kind Regards,
-Greg

Gregory Haskins

Acked-by

2009-11-03 21:40 UTC #3 lore raw

In reply to Steven Rostedt

Quoted 1 line

Quoted 1 line
Quoted 1 line
On 11/3/2009 at 11:41 AM, in message

<[email protected]>, Steven Rostedt

Quoted 19 lines · <[email protected]> wrote:

Greg,
I believe this was mostly your code. Can you review this change.
Thanks,
-- Steve
Quoted 9 lines · Rusty Russell
find_lowest_rq() wants to call pick_optimal_cpu() on the intersection of sched_domain_span(sd) and lowest_mask. Rather than doing a cpus_and into a temporary, we can open-code it.
This actually makes the code slightly clearer, IMHO.
Signed-off-by Rusty Russell <[email protected]>
To: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>

I am not sure that I agree that its "clearer", but I do like the fact that the potentially nasty dynamic mask allocation is removed from the fast path.

I checked the logic, and it does appear to be functionally equivalent to the original.

Acked-by Gregory Haskins <[email protected]>

Quoted 98 lines

---
 kernel/sched_rt.c |   59 +++++++++++++++++++++---------------------------------
 1 file changed, 23 insertions(+), 36 deletions(-)

kernel/sched_rt.c +23 ~~-36~~

@@ -1115,29 +1115,12 @@ static struct task_struct *pick_next_hig
 
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
 
-static inline int pick_optimal_cpu(int this_cpu,
-				   const struct cpumask *mask)
-{
-	int first;
-
-	/* "this_cpu" is cheaper to preempt than a remote processor */
-	if ((this_cpu != -1) && cpumask_test_cpu(this_cpu, mask))
-		return this_cpu;
-
-	first = cpumask_first(mask);
-	if (first < nr_cpu_ids)
-		return first;
-
-	return -1;
-}
-
 static int find_lowest_rq(struct task_struct *task)
 {
 	struct sched_domain *sd;
 	struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
 	int this_cpu = smp_processor_id();
 	int cpu      = task_cpu(task);
-	cpumask_var_t domain_mask;
 
 	if (task->rt.nr_cpus_allowed == 1)
 		return -1; /* No other targets possible */

@@ -1167,28 +1150,26 @@ static int find_lowest_rq(struct task_st
 	 * Otherwise, we consult the sched_domains span maps to figure
 	 * out which cpu is logically closest to our hot cache data.
 	 */
-	if (this_cpu == cpu)
-		this_cpu = -1; /* Skip this_cpu opt if the same */
+	if (!cpumask_test_cpu(this_cpu, lowest_mask))
+		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
 
-	if (alloc_cpumask_var(&domain_mask, GFP_ATOMIC)) {
-		for_each_domain(cpu, sd) {
-			if (sd->flags & SD_WAKE_AFFINE) {
-				int best_cpu;
+	for_each_domain(cpu, sd) {
+		if (sd->flags & SD_WAKE_AFFINE) {
+			int best_cpu;
 
-				cpumask_and(domain_mask,
-					    sched_domain_span(sd),
-					    lowest_mask);
+			/*
+			 * "this_cpu" is cheaper to preempt than a
+			 * remote processor.
+			 */
+			if (this_cpu != -1 &&
+			    cpumask_test_cpu(this_cpu, sched_domain_span(sd)))
+				return this_cpu;
 
-				best_cpu = pick_optimal_cpu(this_cpu,
-							    domain_mask);
-
-				if (best_cpu != -1) {
-					free_cpumask_var(domain_mask);
-					return best_cpu;
-				}
-			}
+			best_cpu = cpumask_first_and(lowest_mask,
+						     sched_domain_span(sd));
+			if (best_cpu < nr_cpu_ids)
+				return best_cpu;
 		}
-		free_cpumask_var(domain_mask);
 	}
 
 	/*

@@ -1196,7 +1177,13 @@ static int find_lowest_rq(struct task_st
 	 * just give the caller *something* to work with from the compatible
 	 * locations.
 	 */
-	return pick_optimal_cpu(this_cpu, lowest_mask);
+	if (this_cpu != -1)
+		return this_cpu;
+
+	cpu = cpumask_any(lowest_mask);
+	if (cpu < nr_cpu_ids)
+		return cpu;
+	return -1;
 }
 
 /* Will lock the rq it finds */

tip-bot for Rusty Russell

author

2009-11-04 15:26 UTC #4 lore raw

[tip:sched/core] cpumask: Simplify sched_rt.c

In reply to Rusty Russell

Commit-ID:  e2c880630438f80b474378d5487b511b07665051
Gitweb:     http://git.kernel.org/tip/e2c880630438f80b474378d5487b511b07665051
Author:     Rusty Russell <[email protected]>
AuthorDate: Tue, 3 Nov 2009 14:53:15 +1030
Committer:  Ingo Molnar <[email protected]>
CommitDate: Wed, 4 Nov 2009 13:16:38 +0100

cpumask: Simplify sched_rt.c

find_lowest_rq() wants to call pick_optimal_cpu() on the intersection of sched_domain_span(sd) and lowest_mask. Rather than doing a cpus_and into a temporary, we can open-code it.

This actually makes the code slightly clearer, IMHO.

Signed-off-by Rusty Russell <[email protected]>

Acked-by Gregory Haskins <[email protected]>

Cc Steven Rostedt <[email protected]>

LKML-Reference: <[email protected]>

Signed-off-by Ingo Molnar <[email protected]>

---
 kernel/sched_rt.c |   61 ++++++++++++++++++++--------------------------------
 1 files changed, 24 insertions(+), 37 deletions(-)

kernel/sched_rt.c +24 ~~-37~~

index a4d790c..5c5fef3 100644
@@ -1153,29 +1153,12 @@ static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
 
 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
 
-static inline int pick_optimal_cpu(int this_cpu,
-				   const struct cpumask *mask)
-{
-	int first;
-
-	/* "this_cpu" is cheaper to preempt than a remote processor */
-	if ((this_cpu != -1) && cpumask_test_cpu(this_cpu, mask))
-		return this_cpu;
-
-	first = cpumask_first(mask);
-	if (first < nr_cpu_ids)
-		return first;
-
-	return -1;
-}
-
 static int find_lowest_rq(struct task_struct *task)
 {
 	struct sched_domain *sd;
 	struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
 	int this_cpu = smp_processor_id();
 	int cpu      = task_cpu(task);
-	cpumask_var_t domain_mask;
 
 	if (task->rt.nr_cpus_allowed == 1)
 		return -1; /* No other targets possible */

@@ -1198,28 +1181,26 @@ static int find_lowest_rq(struct task_struct *task)
 	 * Otherwise, we consult the sched_domains span maps to figure
 	 * out which cpu is logically closest to our hot cache data.
 	 */
-	if (this_cpu == cpu)
-		this_cpu = -1; /* Skip this_cpu opt if the same */
-
-	if (alloc_cpumask_var(&domain_mask, GFP_ATOMIC)) {
-		for_each_domain(cpu, sd) {
-			if (sd->flags & SD_WAKE_AFFINE) {
-				int best_cpu;
+	if (!cpumask_test_cpu(this_cpu, lowest_mask))
+		this_cpu = -1; /* Skip this_cpu opt if not among lowest */
 
-				cpumask_and(domain_mask,
-					    sched_domain_span(sd),
-					    lowest_mask);
+	for_each_domain(cpu, sd) {
+		if (sd->flags & SD_WAKE_AFFINE) {
+			int best_cpu;
 
-				best_cpu = pick_optimal_cpu(this_cpu,
-							    domain_mask);
-
-				if (best_cpu != -1) {
-					free_cpumask_var(domain_mask);
-					return best_cpu;
-				}
-			}
+			/*
+			 * "this_cpu" is cheaper to preempt than a
+			 * remote processor.
+			 */
+			if (this_cpu != -1 &&
+			    cpumask_test_cpu(this_cpu, sched_domain_span(sd)))
+				return this_cpu;
+
+			best_cpu = cpumask_first_and(lowest_mask,
+						     sched_domain_span(sd));
+			if (best_cpu < nr_cpu_ids)
+				return best_cpu;
 		}
-		free_cpumask_var(domain_mask);
 	}
 
 	/*

@@ -1227,7 +1208,13 @@ static int find_lowest_rq(struct task_struct *task)
 	 * just give the caller *something* to work with from the compatible
 	 * locations.
 	 */
-	return pick_optimal_cpu(this_cpu, lowest_mask);
+	if (this_cpu != -1)
+		return this_cpu;
+
+	cpu = cpumask_any(lowest_mask);
+	if (cpu < nr_cpu_ids)
+		return cpu;
+	return -1;
 }
 
 /* Will lock the rq it finds */