diff mbox series

[v6,3/3] mm/mempolicy: Support memory hotplug in weighted interleave

Message ID 20250404074623.1179-4-rakie.kim@sk.com (mailing list archive)
State New
Headers show
Series Enhance sysfs handling for memory hotplug in weighted interleave | expand

Commit Message

Rakie Kim April 4, 2025, 7:46 a.m. UTC 
The weighted interleave policy distributes page allocations across multiple
NUMA nodes based on their performance weight, thereby improving memory
bandwidth utilization. The weight values for each node are configured
through sysfs.

Previously, sysfs entries for configuring weighted interleave were created
for all possible nodes (N_POSSIBLE) at initialization, including nodes that
might not have memory. However, not all nodes in N_POSSIBLE are usable at
runtime, as some may remain memoryless or offline.
This led to sysfs entries being created for unusable nodes, causing
potential misconfiguration issues.

To address this issue, this patch modifies the sysfs creation logic to:
1) Limit sysfs entries to nodes that are online and have memory, avoiding
   the creation of sysfs entries for nodes that cannot be used.
2) Support memory hotplug by dynamically adding and removing sysfs entries
   based on whether a node transitions into or out of the N_MEMORY state.

Additionally, the patch ensures that sysfs attributes are properly managed
when nodes go offline, preventing stale or redundant entries from persisting
in the system.

By making these changes, the weighted interleave policy now manages its
sysfs entries more efficiently, ensuring that only relevant nodes are
considered for interleaving, and dynamically adapting to memory hotplug
events.

Signed-off-by: Rakie Kim <rakie.kim@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
---
 mm/mempolicy.c | 109 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 86 insertions(+), 23 deletions(-)

Comments

Oscar Salvador April 4, 2025, 8:43 a.m. UTC | #1 
On Fri, Apr 04, 2025 at 04:46:21PM +0900, Rakie Kim wrote:
> The weighted interleave policy distributes page allocations across multiple
> NUMA nodes based on their performance weight, thereby improving memory
> bandwidth utilization. The weight values for each node are configured
> through sysfs.
> 
> Previously, sysfs entries for configuring weighted interleave were created
> for all possible nodes (N_POSSIBLE) at initialization, including nodes that
> might not have memory. However, not all nodes in N_POSSIBLE are usable at
> runtime, as some may remain memoryless or offline.
> This led to sysfs entries being created for unusable nodes, causing
> potential misconfiguration issues.
> 
> To address this issue, this patch modifies the sysfs creation logic to:
> 1) Limit sysfs entries to nodes that are online and have memory, avoiding
>    the creation of sysfs entries for nodes that cannot be used.
> 2) Support memory hotplug by dynamically adding and removing sysfs entries
>    based on whether a node transitions into or out of the N_MEMORY state.
> 
> Additionally, the patch ensures that sysfs attributes are properly managed
> when nodes go offline, preventing stale or redundant entries from persisting
> in the system.
> 
> By making these changes, the weighted interleave policy now manages its
> sysfs entries more efficiently, ensuring that only relevant nodes are
> considered for interleaving, and dynamically adapting to memory hotplug
> events.
> 
> Signed-off-by: Rakie Kim <rakie.kim@sk.com>
> Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
> Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>

For the memory-hotplug bits: Reviewed-by: Oscar Salvador
<osalvador@suse.de<

Just one thing that caught my eye:

Cannot add_weighted_interleave_group be __init? AFAICS, it only gets
called at boot time?
David Hildenbrand April 4, 2025, 8:45 p.m. UTC | #2 
On 04.04.25 09:46, Rakie Kim wrote:
> The weighted interleave policy distributes page allocations across multiple
> NUMA nodes based on their performance weight, thereby improving memory
> bandwidth utilization. The weight values for each node are configured
> through sysfs.
> 
> Previously, sysfs entries for configuring weighted interleave were created
> for all possible nodes (N_POSSIBLE) at initialization, including nodes that
> might not have memory. However, not all nodes in N_POSSIBLE are usable at
> runtime, as some may remain memoryless or offline.
> This led to sysfs entries being created for unusable nodes, causing
> potential misconfiguration issues.
> 
> To address this issue, this patch modifies the sysfs creation logic to:
> 1) Limit sysfs entries to nodes that are online and have memory, avoiding
>     the creation of sysfs entries for nodes that cannot be used.
> 2) Support memory hotplug by dynamically adding and removing sysfs entries
>     based on whether a node transitions into or out of the N_MEMORY state.
> 
> Additionally, the patch ensures that sysfs attributes are properly managed
> when nodes go offline, preventing stale or redundant entries from persisting
> in the system.
> 
> By making these changes, the weighted interleave policy now manages its
> sysfs entries more efficiently, ensuring that only relevant nodes are
> considered for interleaving, and dynamically adapting to memory hotplug
> events.
> 
> Signed-off-by: Rakie Kim <rakie.kim@sk.com>
> Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
> Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
> ---
>   mm/mempolicy.c | 109 ++++++++++++++++++++++++++++++++++++++-----------
>   1 file changed, 86 insertions(+), 23 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 73a9405ff352..f25c2c7f8fcf 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -113,6 +113,7 @@
>   #include <asm/tlbflush.h>
>   #include <asm/tlb.h>
>   #include <linux/uaccess.h>
> +#include <linux/memory.h>
>   
>   #include "internal.h"
>   
> @@ -3390,6 +3391,7 @@ struct iw_node_attr {
>   
>   struct sysfs_wi_group {
>   	struct kobject wi_kobj;
> +	struct mutex kobj_lock;
>   	struct iw_node_attr *nattrs[];
>   };
>   
> @@ -3439,13 +3441,24 @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
>   
>   static void sysfs_wi_node_delete(int nid)
>   {
> -	if (!wi_group->nattrs[nid])
> +	struct iw_node_attr *attr;
> +
> +	if (nid < 0 || nid >= nr_node_ids)
> +		return;
> +
> +	mutex_lock(&wi_group->kobj_lock);
> +	attr = wi_group->nattrs[nid];
> +	if (!attr) {
> +		mutex_unlock(&wi_group->kobj_lock);
>   		return;
> +	}
> +
> +	wi_group->nattrs[nid] = NULL;
> +	mutex_unlock(&wi_group->kobj_lock);
>   
> -	sysfs_remove_file(&wi_group->wi_kobj,
> -			  &wi_group->nattrs[nid]->kobj_attr.attr);
> -	kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
> -	kfree(wi_group->nattrs[nid]);
> +	sysfs_remove_file(&wi_group->wi_kobj, &attr->kobj_attr.attr);
> +	kfree(attr->kobj_attr.attr.name);
> +	kfree(attr);
>   }
>   
>   static void sysfs_wi_release(struct kobject *wi_kobj)
> @@ -3464,35 +3477,80 @@ static const struct kobj_type wi_ktype = {
>   
>   static int sysfs_wi_node_add(int nid)
>   {
> -	struct iw_node_attr *node_attr;
> +	int ret = 0;
>   	char *name;
> +	struct iw_node_attr *new_attr = NULL;
>   
> -	node_attr = kzalloc(sizeof(*node_attr), GFP_KERNEL);
> -	if (!node_attr)
> +	if (nid < 0 || nid >= nr_node_ids) {
> +		pr_err("Invalid node id: %d\n", nid);
> +		return -EINVAL;
> +	}
> +
> +	new_attr = kzalloc(sizeof(struct iw_node_attr), GFP_KERNEL);
> +	if (!new_attr)
>   		return -ENOMEM;
>   
>   	name = kasprintf(GFP_KERNEL, "node%d", nid);
>   	if (!name) {
> -		kfree(node_attr);
> +		kfree(new_attr);
>   		return -ENOMEM;
>   	}
>   
> -	sysfs_attr_init(&node_attr->kobj_attr.attr);
> -	node_attr->kobj_attr.attr.name = name;
> -	node_attr->kobj_attr.attr.mode = 0644;
> -	node_attr->kobj_attr.show = node_show;
> -	node_attr->kobj_attr.store = node_store;
> -	node_attr->nid = nid;
> +	mutex_lock(&wi_group->kobj_lock);
> +	if (wi_group->nattrs[nid]) {
> +		mutex_unlock(&wi_group->kobj_lock);
> +		pr_info("Node [%d] already exists\n", nid);
> +		kfree(new_attr);
> +		kfree(name);
> +		return 0;
> +	}
> +	wi_group->nattrs[nid] = new_attr;
>   
> -	if (sysfs_create_file(&wi_group->wi_kobj, &node_attr->kobj_attr.attr)) {
> -		kfree(node_attr->kobj_attr.attr.name);
> -		kfree(node_attr);
> -		pr_err("failed to add attribute to weighted_interleave\n");
> -		return -ENOMEM;
> +	sysfs_attr_init(&wi_group->nattrs[nid]->kobj_attr.attr);
> +	wi_group->nattrs[nid]->kobj_attr.attr.name = name;
> +	wi_group->nattrs[nid]->kobj_attr.attr.mode = 0644;
> +	wi_group->nattrs[nid]->kobj_attr.show = node_show;
> +	wi_group->nattrs[nid]->kobj_attr.store = node_store;
> +	wi_group->nattrs[nid]->nid = nid;
> +
> +	ret = sysfs_create_file(&wi_group->wi_kobj,
> +				&wi_group->nattrs[nid]->kobj_attr.attr);
> +	if (ret) {
> +		kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
> +		kfree(wi_group->nattrs[nid]);
> +		wi_group->nattrs[nid] = NULL;
> +		pr_err("Failed to add attribute to weighted_interleave: %d\n", ret);
>   	}
> +	mutex_unlock(&wi_group->kobj_lock);
>   
> -	wi_group->nattrs[nid] = node_attr;
> -	return 0;
> +	return ret;
> +}
> +
> +static int wi_node_notifier(struct notifier_block *nb,
> +			       unsigned long action, void *data)
> +{
> +	int err;
> +	struct memory_notify *arg = data;
> +	int nid = arg->status_change_nid;
> +
> +	if (nid < 0)
> +		goto notifier_end;
> +
> +	switch(action) {
> +	case MEM_ONLINE:

MEM_ONLINE is too late, we cannot fail hotplug at that point.

Would MEM_GOING_ONLINE / MEM_CANCEL_ONLINE be better?


> +		err = sysfs_wi_node_add(nid);
> +		if (err) {
> +			pr_err("failed to add sysfs [node%d]\n", nid);
> +			return NOTIFY_BAD;

Note that NOTIFY_BAD includes NOTIFY_STOP_MASK. So you wouldn't call 
other notifiers, but the overall memory onlining would succeed, which is 
bad.

If we don't care about the error (not prevent hotplug) we could only 
pr_warn() and continue. Maybe this (unlikely) case is not a good reason 
to stop memory from getting onlined. OTOH, it will barely ever trigger 
in practice ...
diff mbox series

Patch

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 73a9405ff352..f25c2c7f8fcf 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -113,6 +113,7 @@ 
 #include <asm/tlbflush.h>
 #include <asm/tlb.h>
 #include <linux/uaccess.h>
+#include <linux/memory.h>
 
 #include "internal.h"
 
@@ -3390,6 +3391,7 @@  struct iw_node_attr {
 
 struct sysfs_wi_group {
 	struct kobject wi_kobj;
+	struct mutex kobj_lock;
 	struct iw_node_attr *nattrs[];
 };
 
@@ -3439,13 +3441,24 @@  static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 static void sysfs_wi_node_delete(int nid)
 {
-	if (!wi_group->nattrs[nid])
+	struct iw_node_attr *attr;
+
+	if (nid < 0 || nid >= nr_node_ids)
+		return;
+
+	mutex_lock(&wi_group->kobj_lock);
+	attr = wi_group->nattrs[nid];
+	if (!attr) {
+		mutex_unlock(&wi_group->kobj_lock);
 		return;
+	}
+
+	wi_group->nattrs[nid] = NULL;
+	mutex_unlock(&wi_group->kobj_lock);
 
-	sysfs_remove_file(&wi_group->wi_kobj,
-			  &wi_group->nattrs[nid]->kobj_attr.attr);
-	kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
-	kfree(wi_group->nattrs[nid]);
+	sysfs_remove_file(&wi_group->wi_kobj, &attr->kobj_attr.attr);
+	kfree(attr->kobj_attr.attr.name);
+	kfree(attr);
 }
 
 static void sysfs_wi_release(struct kobject *wi_kobj)
@@ -3464,35 +3477,80 @@  static const struct kobj_type wi_ktype = {
 
 static int sysfs_wi_node_add(int nid)
 {
-	struct iw_node_attr *node_attr;
+	int ret = 0;
 	char *name;
+	struct iw_node_attr *new_attr = NULL;
 
-	node_attr = kzalloc(sizeof(*node_attr), GFP_KERNEL);
-	if (!node_attr)
+	if (nid < 0 || nid >= nr_node_ids) {
+		pr_err("Invalid node id: %d\n", nid);
+		return -EINVAL;
+	}
+
+	new_attr = kzalloc(sizeof(struct iw_node_attr), GFP_KERNEL);
+	if (!new_attr)
 		return -ENOMEM;
 
 	name = kasprintf(GFP_KERNEL, "node%d", nid);
 	if (!name) {
-		kfree(node_attr);
+		kfree(new_attr);
 		return -ENOMEM;
 	}
 
-	sysfs_attr_init(&node_attr->kobj_attr.attr);
-	node_attr->kobj_attr.attr.name = name;
-	node_attr->kobj_attr.attr.mode = 0644;
-	node_attr->kobj_attr.show = node_show;
-	node_attr->kobj_attr.store = node_store;
-	node_attr->nid = nid;
+	mutex_lock(&wi_group->kobj_lock);
+	if (wi_group->nattrs[nid]) {
+		mutex_unlock(&wi_group->kobj_lock);
+		pr_info("Node [%d] already exists\n", nid);
+		kfree(new_attr);
+		kfree(name);
+		return 0;
+	}
+	wi_group->nattrs[nid] = new_attr;
 
-	if (sysfs_create_file(&wi_group->wi_kobj, &node_attr->kobj_attr.attr)) {
-		kfree(node_attr->kobj_attr.attr.name);
-		kfree(node_attr);
-		pr_err("failed to add attribute to weighted_interleave\n");
-		return -ENOMEM;
+	sysfs_attr_init(&wi_group->nattrs[nid]->kobj_attr.attr);
+	wi_group->nattrs[nid]->kobj_attr.attr.name = name;
+	wi_group->nattrs[nid]->kobj_attr.attr.mode = 0644;
+	wi_group->nattrs[nid]->kobj_attr.show = node_show;
+	wi_group->nattrs[nid]->kobj_attr.store = node_store;
+	wi_group->nattrs[nid]->nid = nid;
+
+	ret = sysfs_create_file(&wi_group->wi_kobj,
+				&wi_group->nattrs[nid]->kobj_attr.attr);
+	if (ret) {
+		kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
+		kfree(wi_group->nattrs[nid]);
+		wi_group->nattrs[nid] = NULL;
+		pr_err("Failed to add attribute to weighted_interleave: %d\n", ret);
 	}
+	mutex_unlock(&wi_group->kobj_lock);
 
-	wi_group->nattrs[nid] = node_attr;
-	return 0;
+	return ret;
+}
+
+static int wi_node_notifier(struct notifier_block *nb,
+			       unsigned long action, void *data)
+{
+	int err;
+	struct memory_notify *arg = data;
+	int nid = arg->status_change_nid;
+
+	if (nid < 0)
+		goto notifier_end;
+
+	switch(action) {
+	case MEM_ONLINE:
+		err = sysfs_wi_node_add(nid);
+		if (err) {
+			pr_err("failed to add sysfs [node%d]\n", nid);
+			return NOTIFY_BAD;
+		}
+		break;
+	case MEM_OFFLINE:
+		sysfs_wi_node_delete(nid);
+		break;
+	}
+
+notifier_end:
+	return NOTIFY_OK;
 }
 
 static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
@@ -3503,13 +3561,17 @@  static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 			GFP_KERNEL);
 	if (!wi_group)
 		return -ENOMEM;
+	mutex_init(&wi_group->kobj_lock);
 
 	err = kobject_init_and_add(&wi_group->wi_kobj, &wi_ktype, mempolicy_kobj,
 				   "weighted_interleave");
 	if (err)
 		goto err_out;
 
-	for_each_node_state(nid, N_POSSIBLE) {
+	for_each_online_node(nid) {
+		if (!node_state(nid, N_MEMORY))
+			continue;
+
 		err = sysfs_wi_node_add(nid);
 		if (err) {
 			pr_err("failed to add sysfs [node%d]\n", nid);
@@ -3517,6 +3579,7 @@  static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 		}
 	}
 
+	hotplug_memory_notifier(wi_node_notifier, DEFAULT_CALLBACK_PRI);
 	return 0;
 
 err_del: