[PATCH -next 0/3] Some optimizations about cpuset

[PATCH -next 0/3] Some optimizations about cpuset

[Chen Ridong]

Chen Ridong (3):
  cgroup/cpuset: Correct invalid remote parition prs
  cgroup/cpuset: remove fetch_xcpus
  cgroup/cpuset: remove use_parent_ecpus of cpuset

 kernel/cgroup/cpuset.c | 85 +++++++++++++++---------------------------
 1 file changed, 30 insertions(+), 55 deletions(-)

-- 
2.34.1

[PATCH -next 1/3] cgroup/cpuset: Correct invalid remote parition prs

[Chen Ridong]

When enable a remote partition, I found that:

cd /sys/fs/cgroup/
mkdir test
mkdir test/test1
echo +cpuset > cgroup.subtree_control
echo +cpuset >  test/cgroup.subtree_control
echo 3 > test/test1/cpuset.cpus
echo root > test/test1/cpuset.cpus.partition
cat test/test1/cpuset.cpus.partition
root invalid (Parent is not a partition root)

The parent of a remote partition could not be a root. This is due to the
emtpy effective_xcpus. It would be better to prompt the message "invalid
cpu list in cpuset.cpus.exclusive".

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 42 +++++++++++++++++++++++-------------------
 1 file changed, 23 insertions(+), 19 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index e34fd6108b06..fdd5346616d3 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -80,6 +80,7 @@ enum prs_errcode {
 	PERR_HOTPLUG,
 	PERR_CPUSEMPTY,
 	PERR_HKEEPING,
+	PERR_PMT,
 };
 
 static const char * const perr_strings[] = {
@@ -91,6 +92,7 @@ static const char * const perr_strings[] = {
 	[PERR_HOTPLUG]   = "No cpu available due to hotplug",
 	[PERR_CPUSEMPTY] = "cpuset.cpus and cpuset.cpus.exclusive are empty",
 	[PERR_HKEEPING]  = "partition config conflicts with housekeeping setup",
+	[PERR_PMT]       = "Enable partition not permitted",
 };
 
 struct cpuset {
@@ -1669,7 +1671,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
 	 * The user must have sysadmin privilege.
 	 */
 	if (!capable(CAP_SYS_ADMIN))
-		return 0;
+		return PERR_PMT;
 
 	/*
 	 * The requested exclusive_cpus must not be allocated to other
@@ -1683,7 +1685,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
 	if (cpumask_empty(tmp->new_cpus) ||
 	    cpumask_intersects(tmp->new_cpus, subpartitions_cpus) ||
 	    cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
-		return 0;
+		return PERR_INVCPUS;
 
 	spin_lock_irq(&callback_lock);
 	isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
@@ -1698,7 +1700,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
 	 */
 	update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
 	update_sibling_cpumasks(&top_cpuset, NULL, tmp);
-	return 1;
+	return 0;
 }
 
 /*
@@ -3151,24 +3153,26 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 		goto out;
 
 	if (!old_prs) {
-		enum partition_cmd cmd = (new_prs == PRS_ROOT)
-				       ? partcmd_enable : partcmd_enablei;
-
 		/*
-		 * cpus_allowed and exclusive_cpus cannot be both empty.
-		 */
-		if (xcpus_empty(cs)) {
-			err = PERR_CPUSEMPTY;
-			goto out;
-		}
+		* If parent is valid partition, enable local partiion.
+		* Otherwise, enable a remote partition.
+		*/
+		if (is_partition_valid(parent)) {
+			enum partition_cmd cmd = (new_prs == PRS_ROOT)
+					       ? partcmd_enable : partcmd_enablei;
 
-		err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
-		/*
-		 * If an attempt to become local partition root fails,
-		 * try to become a remote partition root instead.
-		 */
-		if (err && remote_partition_enable(cs, new_prs, &tmpmask))
-			err = 0;
+			/*
+			 * cpus_allowed and exclusive_cpus cannot be both empty.
+			 */
+			if (xcpus_empty(cs)) {
+				err = PERR_CPUSEMPTY;
+				goto out;
+			}
+
+			err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
+		} else {
+			err = remote_partition_enable(cs, new_prs, &tmpmask);
+		}
 	} else if (old_prs && new_prs) {
 		/*
 		 * A change in load balance state only, no change in cpumasks.
-- 
2.34.1

[PATCH -next 2/3] cgroup/cpuset: remove fetch_xcpus

[Chen Ridong]

Both fetch_xcpus and user_xcpus functions are used to retrieve the value
of exclusive_cpus. If exclusive_cpus is not set, cpus_allowed is the
implicit value used as exclusive in a local partition. I can not imagine
a scenario where effective_xcpus is not empty when exclusive_cpus is
empty. Therefore, I suggest removing the fetch_xcpus function.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index fdd5346616d3..8be0259065f5 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -771,13 +771,6 @@ static inline bool xcpus_empty(struct cpuset *cs)
 	       cpumask_empty(cs->exclusive_cpus);
 }
 
-static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
-{
-	return !cpumask_empty(cs->exclusive_cpus) ? cs->exclusive_cpus :
-	       cpumask_empty(cs->effective_xcpus) ? cs->cpus_allowed
-						  : cs->effective_xcpus;
-}
-
 /*
  * cpusets_are_exclusive() - check if two cpusets are exclusive
  *
@@ -785,8 +778,8 @@ static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
  */
 static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
 {
-	struct cpumask *xcpus1 = fetch_xcpus(cs1);
-	struct cpumask *xcpus2 = fetch_xcpus(cs2);
+	struct cpumask *xcpus1 = user_xcpus(cs1);
+	struct cpumask *xcpus2 = user_xcpus(cs2);
 
 	if (cpumask_intersects(xcpus1, xcpus2))
 		return false;
@@ -2585,7 +2578,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 		invalidate = true;
 		rcu_read_lock();
 		cpuset_for_each_child(cp, css, parent) {
-			struct cpumask *xcpus = fetch_xcpus(trialcs);
+			struct cpumask *xcpus = user_xcpus(trialcs);
 
 			if (is_partition_valid(cp) &&
 			    cpumask_intersects(xcpus, cp->effective_xcpus)) {
-- 
2.34.1

[PATCH -next 3/3] cgroup/cpuset: remove use_parent_ecpus of cpuset

[Chen Ridong]

use_parent_ecpus is used to track whether the children are using the
parent's effective_cpus. When a parent's effective_cpus is changed
due to changes in a child partition's effective_xcpus, any child
using parent'effective_cpus must call update_cpumasks_hier. However,
if a child is not a valid partition, it is sufficient to determine
whether to call update_cpumasks_hier based on whether the child's
effective_cpus is going to change. To make the code more succinct,
it is suggested to remove use_parent_ecpus.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 kernel/cgroup/cpuset.c | 30 ++++--------------------------
 1 file changed, 4 insertions(+), 26 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 8be0259065f5..71c24542966b 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -185,12 +185,6 @@ struct cpuset {
 	/* partition root state */
 	int partition_root_state;
 
-	/*
-	 * Default hierarchy only:
-	 * use_parent_ecpus - set if using parent's effective_cpus
-	 */
-	int use_parent_ecpus;
-
 	/*
 	 * number of SCHED_DEADLINE tasks attached to this cpuset, so that we
 	 * know when to rebuild associated root domain bandwidth information.
@@ -1505,11 +1499,8 @@ static void reset_partition_data(struct cpuset *cs)
 		if (is_cpu_exclusive(cs))
 			clear_bit(CS_CPU_EXCLUSIVE, &cs->flags);
 	}
-	if (!cpumask_and(cs->effective_cpus,
-			 parent->effective_cpus, cs->cpus_allowed)) {
-		cs->use_parent_ecpus = true;
+	if (!cpumask_and(cs->effective_cpus, parent->effective_cpus, cs->cpus_allowed))
 		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
-	}
 }
 
 /*
@@ -1683,8 +1674,6 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
 	spin_lock_irq(&callback_lock);
 	isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
 	list_add(&cs->remote_sibling, &remote_children);
-	if (cs->use_parent_ecpus)
-		cs->use_parent_ecpus = false;
 	spin_unlock_irq(&callback_lock);
 	update_unbound_workqueue_cpumask(isolcpus_updated);
 
@@ -2309,13 +2298,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
 		 * it is a partition root that has explicitly distributed
 		 * out all its CPUs.
 		 */
-		if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus)) {
+		if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus))
 			cpumask_copy(tmp->new_cpus, parent->effective_cpus);
-			if (!cp->use_parent_ecpus)
-				cp->use_parent_ecpus = true;
-		} else if (cp->use_parent_ecpus) {
-			cp->use_parent_ecpus = false;
-		}
 
 		if (remote)
 			goto get_css;
@@ -2452,8 +2436,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
 	 * Check all its siblings and call update_cpumasks_hier()
 	 * if their effective_cpus will need to be changed.
 	 *
-	 * With the addition of effective_xcpus which is a subset of
-	 * cpus_allowed. It is possible a change in parent's effective_cpus
+	 * It is possible a change in parent's effective_cpus
 	 * due to a change in a child partition's effective_xcpus will impact
 	 * its siblings even if they do not inherit parent's effective_cpus
 	 * directly.
@@ -2467,8 +2450,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
 	cpuset_for_each_child(sibling, pos_css, parent) {
 		if (sibling == cs)
 			continue;
-		if (!sibling->use_parent_ecpus &&
-		    !is_partition_valid(sibling)) {
+		if (!is_partition_valid(sibling)) {
 			compute_effective_cpumask(tmp->new_cpus, sibling,
 						  parent);
 			if (cpumask_equal(tmp->new_cpus, sibling->effective_cpus))
@@ -4128,7 +4110,6 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 	if (is_in_v2_mode()) {
 		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
 		cs->effective_mems = parent->effective_mems;
-		cs->use_parent_ecpus = true;
 	}
 	spin_unlock_irq(&callback_lock);
 
@@ -4194,9 +4175,6 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
 	    is_sched_load_balance(cs))
 		update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
 
-	if (cs->use_parent_ecpus)
-		cs->use_parent_ecpus = false;
-
 	cpuset_dec();
 	clear_bit(CS_ONLINE, &cs->flags);
 
-- 
2.34.1

Re: [PATCH -next 1/3] cgroup/cpuset: Correct invalid remote parition prs

[Waiman Long]

On 8/16/24 04:27, Chen Ridong wrote:
> When enable a remote partition, I found that:
>
> cd /sys/fs/cgroup/
> mkdir test
> mkdir test/test1
> echo +cpuset > cgroup.subtree_control
> echo +cpuset >  test/cgroup.subtree_control
> echo 3 > test/test1/cpuset.cpus
> echo root > test/test1/cpuset.cpus.partition
> cat test/test1/cpuset.cpus.partition
> root invalid (Parent is not a partition root)
>
> The parent of a remote partition could not be a root. This is due to the
> emtpy effective_xcpus. It would be better to prompt the message "invalid
> cpu list in cpuset.cpus.exclusive".
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 42 +++++++++++++++++++++++-------------------
>   1 file changed, 23 insertions(+), 19 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index e34fd6108b06..fdd5346616d3 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -80,6 +80,7 @@ enum prs_errcode {
>   	PERR_HOTPLUG,
>   	PERR_CPUSEMPTY,
>   	PERR_HKEEPING,
> +	PERR_PMT,
>   };
>   
>   static const char * const perr_strings[] = {
> @@ -91,6 +92,7 @@ static const char * const perr_strings[] = {
>   	[PERR_HOTPLUG]   = "No cpu available due to hotplug",
>   	[PERR_CPUSEMPTY] = "cpuset.cpus and cpuset.cpus.exclusive are empty",
>   	[PERR_HKEEPING]  = "partition config conflicts with housekeeping setup",
> +	[PERR_PMT]       = "Enable partition not permitted",
>   };
>   
>   struct cpuset {
> @@ -1669,7 +1671,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
>   	 * The user must have sysadmin privilege.
>   	 */
>   	if (!capable(CAP_SYS_ADMIN))
> -		return 0;
> +		return PERR_PMT;
>   
>   	/*
>   	 * The requested exclusive_cpus must not be allocated to other
> @@ -1683,7 +1685,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
>   	if (cpumask_empty(tmp->new_cpus) ||
>   	    cpumask_intersects(tmp->new_cpus, subpartitions_cpus) ||
>   	    cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
> -		return 0;
> +		return PERR_INVCPUS;
>   
>   	spin_lock_irq(&callback_lock);
>   	isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
> @@ -1698,7 +1700,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
>   	 */
>   	update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
>   	update_sibling_cpumasks(&top_cpuset, NULL, tmp);
> -	return 1;
> +	return 0;
>   }

Since you are changing the meaning of the function returned value, you 
should also update the return value comment as well.

>   
>   /*
> @@ -3151,24 +3153,26 @@ static int update_prstate(struct cpuset *cs, int new_prs)
>   		goto out;
>   
>   	if (!old_prs) {
> -		enum partition_cmd cmd = (new_prs == PRS_ROOT)
> -				       ? partcmd_enable : partcmd_enablei;
> -
>   		/*
> -		 * cpus_allowed and exclusive_cpus cannot be both empty.
> -		 */
> -		if (xcpus_empty(cs)) {
> -			err = PERR_CPUSEMPTY;
> -			goto out;
> -		}
> +		* If parent is valid partition, enable local partiion.
> +		* Otherwise, enable a remote partition.
> +		*/
> +		if (is_partition_valid(parent)) {
> +			enum partition_cmd cmd = (new_prs == PRS_ROOT)
> +					       ? partcmd_enable : partcmd_enablei;
>   
> -		err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
> -		/*
> -		 * If an attempt to become local partition root fails,
> -		 * try to become a remote partition root instead.
> -		 */
> -		if (err && remote_partition_enable(cs, new_prs, &tmpmask))
> -			err = 0;
> +			/*
> +			 * cpus_allowed and exclusive_cpus cannot be both empty.
> +			 */
> +			if (xcpus_empty(cs)) {
> +				err = PERR_CPUSEMPTY;
> +				goto out;
> +			}

The xcpus_empty() check should be done for both local and remote partition.

Cheers,
Longman

> +
> +			err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
> +		} else {
> +			err = remote_partition_enable(cs, new_prs, &tmpmask);
> +		}
>   	} else if (old_prs && new_prs) {
>   		/*
>   		 * A change in load balance state only, no change in cpumasks.

Re: [PATCH -next 1/3] cgroup/cpuset: Correct invalid remote parition prs

[Waiman Long]

On 8/18/24 22:14, Waiman Long wrote:
>
> On 8/16/24 04:27, Chen Ridong wrote:
>> When enable a remote partition, I found that:
>>
>> cd /sys/fs/cgroup/
>> mkdir test
>> mkdir test/test1
>> echo +cpuset > cgroup.subtree_control
>> echo +cpuset >  test/cgroup.subtree_control
>> echo 3 > test/test1/cpuset.cpus
>> echo root > test/test1/cpuset.cpus.partition
>> cat test/test1/cpuset.cpus.partition
>> root invalid (Parent is not a partition root)
>>
>> The parent of a remote partition could not be a root. This is due to the
>> emtpy effective_xcpus. It would be better to prompt the message "invalid
>> cpu list in cpuset.cpus.exclusive".
>>
>> Signed-off-by: Chen Ridong <chenridong@huawei.com>
>> ---
>>   kernel/cgroup/cpuset.c | 42 +++++++++++++++++++++++-------------------
>>   1 file changed, 23 insertions(+), 19 deletions(-)
>>
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index e34fd6108b06..fdd5346616d3 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -80,6 +80,7 @@ enum prs_errcode {
>>       PERR_HOTPLUG,
>>       PERR_CPUSEMPTY,
>>       PERR_HKEEPING,
>> +    PERR_PMT,

One more thing, the "PMT" acronym for the error code is hard to decode. 
I will suggest you either use the "PERMISSION" or "ACCESS" like the 
EACCESS errno.

Cheers,
Longman

>>   };
>>     static const char * const perr_strings[] = {
>> @@ -91,6 +92,7 @@ static const char * const perr_strings[] = {
>>       [PERR_HOTPLUG]   = "No cpu available due to hotplug",
>>       [PERR_CPUSEMPTY] = "cpuset.cpus and cpuset.cpus.exclusive are 
>> empty",
>>       [PERR_HKEEPING]  = "partition config conflicts with 
>> housekeeping setup",
>> +    [PERR_PMT]       = "Enable partition not permitted",
>>   };
>>     struct cpuset {
>> @@ -1669,7 +1671,7 @@ static int remote_partition_enable(struct 
>> cpuset *cs, int new_prs,
>>        * The user must have sysadmin privilege.
>>        */
>>       if (!capable(CAP_SYS_ADMIN))
>> -        return 0;
>> +        return PERR_PMT;
>>         /*
>>        * The requested exclusive_cpus must not be allocated to other
>> @@ -1683,7 +1685,7 @@ static int remote_partition_enable(struct 
>> cpuset *cs, int new_prs,
>>       if (cpumask_empty(tmp->new_cpus) ||
>>           cpumask_intersects(tmp->new_cpus, subpartitions_cpus) ||
>>           cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
>> -        return 0;
>> +        return PERR_INVCPUS;
>>         spin_lock_irq(&callback_lock);
>>       isolcpus_updated = partition_xcpus_add(new_prs, NULL, 
>> tmp->new_cpus);
>> @@ -1698,7 +1700,7 @@ static int remote_partition_enable(struct 
>> cpuset *cs, int new_prs,
>>        */
>>       update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
>>       update_sibling_cpumasks(&top_cpuset, NULL, tmp);
>> -    return 1;
>> +    return 0;
>>   }
>
> Since you are changing the meaning of the function returned value, you 
> should also update the return value comment as well.
>
>>     /*
>> @@ -3151,24 +3153,26 @@ static int update_prstate(struct cpuset *cs, 
>> int new_prs)
>>           goto out;
>>         if (!old_prs) {
>> -        enum partition_cmd cmd = (new_prs == PRS_ROOT)
>> -                       ? partcmd_enable : partcmd_enablei;
>> -
>>           /*
>> -         * cpus_allowed and exclusive_cpus cannot be both empty.
>> -         */
>> -        if (xcpus_empty(cs)) {
>> -            err = PERR_CPUSEMPTY;
>> -            goto out;
>> -        }
>> +        * If parent is valid partition, enable local partiion.
>> +        * Otherwise, enable a remote partition.
>> +        */
>> +        if (is_partition_valid(parent)) {
>> +            enum partition_cmd cmd = (new_prs == PRS_ROOT)
>> +                           ? partcmd_enable : partcmd_enablei;
>>   -        err = update_parent_effective_cpumask(cs, cmd, NULL, 
>> &tmpmask);
>> -        /*
>> -         * If an attempt to become local partition root fails,
>> -         * try to become a remote partition root instead.
>> -         */
>> -        if (err && remote_partition_enable(cs, new_prs, &tmpmask))
>> -            err = 0;
>> +            /*
>> +             * cpus_allowed and exclusive_cpus cannot be both empty.
>> +             */
>> +            if (xcpus_empty(cs)) {
>> +                err = PERR_CPUSEMPTY;
>> +                goto out;
>> +            }
>
> The xcpus_empty() check should be done for both local and remote 
> partition.
>
> Cheers,
> Longman
>
>> +
>> +            err = update_parent_effective_cpumask(cs, cmd, NULL, 
>> &tmpmask);
>> +        } else {
>> +            err = remote_partition_enable(cs, new_prs, &tmpmask);
>> +        }
>>       } else if (old_prs && new_prs) {
>>           /*
>>            * A change in load balance state only, no change in cpumasks.

Re: [PATCH -next 1/3] cgroup/cpuset: Correct invalid remote parition prs

[chenridong]

On 2024/8/19 10:18, Waiman Long wrote:
> On 8/18/24 22:14, Waiman Long wrote:
>>
>> On 8/16/24 04:27, Chen Ridong wrote:
>>> When enable a remote partition, I found that:
>>>
>>> cd /sys/fs/cgroup/
>>> mkdir test
>>> mkdir test/test1
>>> echo +cpuset > cgroup.subtree_control
>>> echo +cpuset >  test/cgroup.subtree_control
>>> echo 3 > test/test1/cpuset.cpus
>>> echo root > test/test1/cpuset.cpus.partition
>>> cat test/test1/cpuset.cpus.partition
>>> root invalid (Parent is not a partition root)
>>>
>>> The parent of a remote partition could not be a root. This is due to the
>>> emtpy effective_xcpus. It would be better to prompt the message "invalid
>>> cpu list in cpuset.cpus.exclusive".
>>>
>>> Signed-off-by: Chen Ridong <chenridong@huawei.com>
>>> ---
>>>   kernel/cgroup/cpuset.c | 42 +++++++++++++++++++++++-------------------
>>>   1 file changed, 23 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>>> index e34fd6108b06..fdd5346616d3 100644
>>> --- a/kernel/cgroup/cpuset.c
>>> +++ b/kernel/cgroup/cpuset.c
>>> @@ -80,6 +80,7 @@ enum prs_errcode {
>>>       PERR_HOTPLUG,
>>>       PERR_CPUSEMPTY,
>>>       PERR_HKEEPING,
>>> +    PERR_PMT,
> 
> One more thing, the "PMT" acronym for the error code is hard to decode. 
> I will suggest you either use the "PERMISSION" or "ACCESS" like the 
> EACCESS errno.
> 
> Cheers,
> Longman
> 
Thanks, will do.
>>>   };
>>>     static const char * const perr_strings[] = {
>>> @@ -91,6 +92,7 @@ static const char * const perr_strings[] = {
>>>       [PERR_HOTPLUG]   = "No cpu available due to hotplug",
>>>       [PERR_CPUSEMPTY] = "cpuset.cpus and cpuset.cpus.exclusive are 
>>> empty",
>>>       [PERR_HKEEPING]  = "partition config conflicts with 
>>> housekeeping setup",
>>> +    [PERR_PMT]       = "Enable partition not permitted",
>>>   };
>>>     struct cpuset {
>>> @@ -1669,7 +1671,7 @@ static int remote_partition_enable(struct 
>>> cpuset *cs, int new_prs,
>>>        * The user must have sysadmin privilege.
>>>        */
>>>       if (!capable(CAP_SYS_ADMIN))
>>> -        return 0;
>>> +        return PERR_PMT;
>>>         /*
>>>        * The requested exclusive_cpus must not be allocated to other
>>> @@ -1683,7 +1685,7 @@ static int remote_partition_enable(struct 
>>> cpuset *cs, int new_prs,
>>>       if (cpumask_empty(tmp->new_cpus) ||
>>>           cpumask_intersects(tmp->new_cpus, subpartitions_cpus) ||
>>>           cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
>>> -        return 0;
>>> +        return PERR_INVCPUS;
>>>         spin_lock_irq(&callback_lock);
>>>       isolcpus_updated = partition_xcpus_add(new_prs, NULL, 
>>> tmp->new_cpus);
>>> @@ -1698,7 +1700,7 @@ static int remote_partition_enable(struct 
>>> cpuset *cs, int new_prs,
>>>        */
>>>       update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
>>>       update_sibling_cpumasks(&top_cpuset, NULL, tmp);
>>> -    return 1;
>>> +    return 0;
>>>   }
>>
>> Since you are changing the meaning of the function returned value, you 
>> should also update the return value comment as well.
>>
Will do.
>>>     /*
>>> @@ -3151,24 +3153,26 @@ static int update_prstate(struct cpuset *cs, 
>>> int new_prs)
>>>           goto out;
>>>         if (!old_prs) {
>>> -        enum partition_cmd cmd = (new_prs == PRS_ROOT)
>>> -                       ? partcmd_enable : partcmd_enablei;
>>> -
>>>           /*
>>> -         * cpus_allowed and exclusive_cpus cannot be both empty.
>>> -         */
>>> -        if (xcpus_empty(cs)) {
>>> -            err = PERR_CPUSEMPTY;
>>> -            goto out;
>>> -        }
>>> +        * If parent is valid partition, enable local partiion.
>>> +        * Otherwise, enable a remote partition.
>>> +        */
>>> +        if (is_partition_valid(parent)) {
>>> +            enum partition_cmd cmd = (new_prs == PRS_ROOT)
>>> +                           ? partcmd_enable : partcmd_enablei;
>>>   -        err = update_parent_effective_cpumask(cs, cmd, NULL, 
>>> &tmpmask);
>>> -        /*
>>> -         * If an attempt to become local partition root fails,
>>> -         * try to become a remote partition root instead.
>>> -         */
>>> -        if (err && remote_partition_enable(cs, new_prs, &tmpmask))
>>> -            err = 0;
>>> +            /*
>>> +             * cpus_allowed and exclusive_cpus cannot be both empty.
>>> +             */
>>> +            if (xcpus_empty(cs)) {
>>> +                err = PERR_CPUSEMPTY;
>>> +                goto out;
>>> +            }
>>
>> The xcpus_empty() check should be done for both local and remote 
>> partition.
>>
>> Cheers,
>> Longman
>>
Thanks, I will do it at V2.

Thanks,
Ridong
>>> +
>>> +            err = update_parent_effective_cpumask(cs, cmd, NULL, 
>>> &tmpmask);
>>> +        } else {
>>> +            err = remote_partition_enable(cs, new_prs, &tmpmask);
>>> +        }
>>>       } else if (old_prs && new_prs) {
>>>           /*
>>>            * A change in load balance state only, no change in cpumasks.
> 
> 

Re: [PATCH -next 2/3] cgroup/cpuset: remove fetch_xcpus

[Saket Kumar Bhaskar]

On Fri, Aug 16, 2024 at 08:27:26AM +0000, Chen Ridong wrote:
> Both fetch_xcpus and user_xcpus functions are used to retrieve the value
> of exclusive_cpus. If exclusive_cpus is not set, cpus_allowed is the
> implicit value used as exclusive in a local partition. I can not imagine
> a scenario where effective_xcpus is not empty when exclusive_cpus is
> empty. Therefore, I suggest removing the fetch_xcpus function.
> 
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>  kernel/cgroup/cpuset.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index fdd5346616d3..8be0259065f5 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -771,13 +771,6 @@ static inline bool xcpus_empty(struct cpuset *cs)
>  	       cpumask_empty(cs->exclusive_cpus);
>  }
>  
> -static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
> -{
> -	return !cpumask_empty(cs->exclusive_cpus) ? cs->exclusive_cpus :
> -	       cpumask_empty(cs->effective_xcpus) ? cs->cpus_allowed
> -						  : cs->effective_xcpus;
> -}
> -
>  /*
>   * cpusets_are_exclusive() - check if two cpusets are exclusive
>   *
> @@ -785,8 +778,8 @@ static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
>   */
>  static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
>  {
> -	struct cpumask *xcpus1 = fetch_xcpus(cs1);
> -	struct cpumask *xcpus2 = fetch_xcpus(cs2);
> +	struct cpumask *xcpus1 = user_xcpus(cs1);
> +	struct cpumask *xcpus2 = user_xcpus(cs2);
>  
>  	if (cpumask_intersects(xcpus1, xcpus2))
>  		return false;
> @@ -2585,7 +2578,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
>  		invalidate = true;
>  		rcu_read_lock();
>  		cpuset_for_each_child(cp, css, parent) {
> -			struct cpumask *xcpus = fetch_xcpus(trialcs);
> +			struct cpumask *xcpus = user_xcpus(trialcs);
>  
>  			if (is_partition_valid(cp) &&
>  			    cpumask_intersects(xcpus, cp->effective_xcpus)) {
> -- 
> 2.34.1
> 

Hi,

In update_cpumask too fetch_xcpus is used. You may want to remove it from there too.

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 40ec4abaf440..1b4ee6403de6 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2587,7 +2587,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
                invalidate = true;
                rcu_read_lock();
                cpuset_for_each_child(cp, css, parent) {
-                       struct cpumask *xcpus = fetch_xcpus(trialcs);
+                       struct cpumask *xcpus = user_xcpus(trialcs);

                        if (is_partition_valid(cp) &&
                            cpumask_intersects(xcpus, cp->effective_xcpus)) {


Reviewed-by: Saket Kumar Bhaskar <skb99@linux.ibm.com> 

Thanks,
Saket

Re: [PATCH -next 2/3] cgroup/cpuset: remove fetch_xcpus

[Waiman Long]

On 8/16/24 04:27, Chen Ridong wrote:
> Both fetch_xcpus and user_xcpus functions are used to retrieve the value
> of exclusive_cpus. If exclusive_cpus is not set, cpus_allowed is the
> implicit value used as exclusive in a local partition. I can not imagine
> a scenario where effective_xcpus is not empty when exclusive_cpus is
> empty. Therefore, I suggest removing the fetch_xcpus function.
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 13 +++----------
>   1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index fdd5346616d3..8be0259065f5 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -771,13 +771,6 @@ static inline bool xcpus_empty(struct cpuset *cs)
>   	       cpumask_empty(cs->exclusive_cpus);
>   }
>   
> -static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
> -{
> -	return !cpumask_empty(cs->exclusive_cpus) ? cs->exclusive_cpus :
> -	       cpumask_empty(cs->effective_xcpus) ? cs->cpus_allowed
> -						  : cs->effective_xcpus;
> -}
> -
>   /*
>    * cpusets_are_exclusive() - check if two cpusets are exclusive
>    *
> @@ -785,8 +778,8 @@ static inline struct cpumask *fetch_xcpus(struct cpuset *cs)
>    */
>   static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
>   {
> -	struct cpumask *xcpus1 = fetch_xcpus(cs1);
> -	struct cpumask *xcpus2 = fetch_xcpus(cs2);
> +	struct cpumask *xcpus1 = user_xcpus(cs1);
> +	struct cpumask *xcpus2 = user_xcpus(cs2);
>   
>   	if (cpumask_intersects(xcpus1, xcpus2))
>   		return false;
> @@ -2585,7 +2578,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
>   		invalidate = true;
>   		rcu_read_lock();
>   		cpuset_for_each_child(cp, css, parent) {
> -			struct cpumask *xcpus = fetch_xcpus(trialcs);
> +			struct cpumask *xcpus = user_xcpus(trialcs);
>   
>   			if (is_partition_valid(cp) &&
>   			    cpumask_intersects(xcpus, cp->effective_xcpus)) {

LGTM.

Reviewed-by: Waiman Long <longman@redhat.com>

Re: [PATCH -next 3/3] cgroup/cpuset: remove use_parent_ecpus of cpuset

[Waiman Long]

On 8/16/24 04:27, Chen Ridong wrote:
> use_parent_ecpus is used to track whether the children are using the
> parent's effective_cpus. When a parent's effective_cpus is changed
> due to changes in a child partition's effective_xcpus, any child
> using parent'effective_cpus must call update_cpumasks_hier. However,
> if a child is not a valid partition, it is sufficient to determine
> whether to call update_cpumasks_hier based on whether the child's
> effective_cpus is going to change. To make the code more succinct,
> it is suggested to remove use_parent_ecpus.
>
> Signed-off-by: Chen Ridong <chenridong@huawei.com>
> ---
>   kernel/cgroup/cpuset.c | 30 ++++--------------------------
>   1 file changed, 4 insertions(+), 26 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 8be0259065f5..71c24542966b 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -185,12 +185,6 @@ struct cpuset {
>   	/* partition root state */
>   	int partition_root_state;
>   
> -	/*
> -	 * Default hierarchy only:
> -	 * use_parent_ecpus - set if using parent's effective_cpus
> -	 */
> -	int use_parent_ecpus;
> -
>   	/*
>   	 * number of SCHED_DEADLINE tasks attached to this cpuset, so that we
>   	 * know when to rebuild associated root domain bandwidth information.
> @@ -1505,11 +1499,8 @@ static void reset_partition_data(struct cpuset *cs)
>   		if (is_cpu_exclusive(cs))
>   			clear_bit(CS_CPU_EXCLUSIVE, &cs->flags);
>   	}
> -	if (!cpumask_and(cs->effective_cpus,
> -			 parent->effective_cpus, cs->cpus_allowed)) {
> -		cs->use_parent_ecpus = true;
> +	if (!cpumask_and(cs->effective_cpus, parent->effective_cpus, cs->cpus_allowed))
>   		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
> -	}
>   }
>   
>   /*
> @@ -1683,8 +1674,6 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
>   	spin_lock_irq(&callback_lock);
>   	isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
>   	list_add(&cs->remote_sibling, &remote_children);
> -	if (cs->use_parent_ecpus)
> -		cs->use_parent_ecpus = false;
>   	spin_unlock_irq(&callback_lock);
>   	update_unbound_workqueue_cpumask(isolcpus_updated);
>   
> @@ -2309,13 +2298,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
>   		 * it is a partition root that has explicitly distributed
>   		 * out all its CPUs.
>   		 */
> -		if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus)) {
> +		if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus))
>   			cpumask_copy(tmp->new_cpus, parent->effective_cpus);
> -			if (!cp->use_parent_ecpus)
> -				cp->use_parent_ecpus = true;
> -		} else if (cp->use_parent_ecpus) {
> -			cp->use_parent_ecpus = false;
> -		}
>   
>   		if (remote)
>   			goto get_css;
> @@ -2452,8 +2436,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
>   	 * Check all its siblings and call update_cpumasks_hier()
>   	 * if their effective_cpus will need to be changed.
>   	 *
> -	 * With the addition of effective_xcpus which is a subset of
> -	 * cpus_allowed. It is possible a change in parent's effective_cpus
> +	 * It is possible a change in parent's effective_cpus
>   	 * due to a change in a child partition's effective_xcpus will impact
>   	 * its siblings even if they do not inherit parent's effective_cpus
>   	 * directly.
> @@ -2467,8 +2450,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
>   	cpuset_for_each_child(sibling, pos_css, parent) {
>   		if (sibling == cs)
>   			continue;
> -		if (!sibling->use_parent_ecpus &&
> -		    !is_partition_valid(sibling)) {
> +		if (!is_partition_valid(sibling)) {
>   			compute_effective_cpumask(tmp->new_cpus, sibling,
>   						  parent);
>   			if (cpumask_equal(tmp->new_cpus, sibling->effective_cpus))
> @@ -4128,7 +4110,6 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
>   	if (is_in_v2_mode()) {
>   		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
>   		cs->effective_mems = parent->effective_mems;
> -		cs->use_parent_ecpus = true;
>   	}
>   	spin_unlock_irq(&callback_lock);
>   
> @@ -4194,9 +4175,6 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
>   	    is_sched_load_balance(cs))
>   		update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
>   
> -	if (cs->use_parent_ecpus)
> -		cs->use_parent_ecpus = false;
> -
>   	cpuset_dec();
>   	clear_bit(CS_ONLINE, &cs->flags);
>   

LGTM

Reviewed-by: Waiman Long <longman@redhat.com>

Re: [PATCH -next 0/3] Some optimizations about cpuset

[Tejun Heo]

On Fri, Aug 16, 2024 at 08:27:24AM +0000, Chen Ridong wrote:
> Chen Ridong (3):
>   cgroup/cpuset: Correct invalid remote parition prs
>   cgroup/cpuset: remove fetch_xcpus
>   cgroup/cpuset: remove use_parent_ecpus of cpuset

Looks like the first patch needs update. I'll wait for the v2 patchset.

Thanks.

-- 
tejun