Gregory Price <gourry.memverge@xxxxxxxxx> writes:
> From: Rakie Kim <rakie.kim@xxxxxx>
>
> This patch provides a way to set interleave weight information under
> sysfs at /sys/kernel/mm/mempolicy/weighted_interleave/nodeN
>
> The sysfs structure is designed as follows.
>
> $ tree /sys/kernel/mm/mempolicy/
> /sys/kernel/mm/mempolicy/ [1]
> └── weighted_interleave [2]
> ├── node0 [3]
> └── node1
>
> Each file above can be explained as follows.
>
> [1] mm/mempolicy: configuration interface for mempolicy subsystem
>
> [2] weighted_interleave/: config interface for weighted interleave policy
>
> [3] weighted_interleave/nodeN: weight for nodeN
>
> If a node value is set to `0`, the system-default value will be used.
> As of this patch, the system-default for all nodes is always 1.
>
> Suggested-by: Huang Ying <ying.huang@xxxxxxxxx>
> Signed-off-by: Rakie Kim <rakie.kim@xxxxxx>
> Signed-off-by: Honggyu Kim <honggyu.kim@xxxxxx>
> Co-developed-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
> Signed-off-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
> Co-developed-by: Hyeongtak Ji <hyeongtak.ji@xxxxxx>
> Signed-off-by: Hyeongtak Ji <hyeongtak.ji@xxxxxx>
> ---
> .../ABI/testing/sysfs-kernel-mm-mempolicy | 4 +
> ...fs-kernel-mm-mempolicy-weighted-interleave | 26 ++
> mm/mempolicy.c | 231 ++++++++++++++++++
> 3 files changed, 261 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-mempolicy
> create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy b/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy
> new file mode 100644
> index 000000000000..2dcf24f4384a
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy
> @@ -0,0 +1,4 @@
> +What: /sys/kernel/mm/mempolicy/
> +Date: December 2023
> +Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx>
> +Description: Interface for Mempolicy
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave b/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave
> new file mode 100644
> index 000000000000..e6a38139bf0f
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave
> @@ -0,0 +1,26 @@
> +What: /sys/kernel/mm/mempolicy/weighted_interleave/
> +Date: December 2023
May be not a big deal. The date should be "January 2024"?
> +Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx>
> +Description: Configuration Interface for the Weighted Interleave policy
> +
> +What: /sys/kernel/mm/mempolicy/weighted_interleave/nodeN
> +Date: December 2023
> +Contact: Linux memory management mailing list <linux-mm@xxxxxxxxx>
> +Description: Weight configuration interface for nodeN
> +
> + The interleave weight for a memory node (N). These weights are
> + utilized by processes which have set their mempolicy to
s/processes/tasks or memory areas/
> + MPOL_WEIGHTED_INTERLEAVE and have opted into global weights by
> + omitting a task-local weight array.
Now, we haven't introduced task-local weight array. So, leave this
until we introduce that?
> +
> + These weights only affect new allocations, and changes at runtime
> + will not cause migrations on already allocated pages.
> +
> + The minimum weight for a node is always 1.
> +
> + Minimum weight: 1
> + Maximum weight: 255
> +
> + Writing an empty string or `0` will reset the weight to the
> + system default. The system default may be set by the kernel
> + or drivers at boot or during hotplug events.
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 10a590ee1c89..ae925216798f 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -131,6 +131,16 @@ static struct mempolicy default_policy = {
>
> static struct mempolicy preferred_node_policy[MAX_NUMNODES];
>
> +/*
> + * iw_table is the sysfs-set interleave weight table, a value of 0 denotes
> + * system-default value should be used. Until system-defaults are implemented,
> + * the system-default is always 1.
> + *
> + * iw_table is RCU protected
> + */
> +static u8 __rcu *iw_table;
> +static DEFINE_MUTEX(iw_table_lock);
> +
> /**
> * numa_nearest_node - Find nearest node by state
> * @node: Node id to start the search
> @@ -3067,3 +3077,224 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
> p += scnprintf(p, buffer + maxlen - p, ":%*pbl",
> nodemask_pr_args(&nodes));
> }
> +
> +#ifdef CONFIG_SYSFS
> +struct iw_node_attr {
> + struct kobj_attribute kobj_attr;
> + int nid;
> +};
> +
> +static ssize_t node_show(struct kobject *kobj, struct kobj_attribute *attr,
> + char *buf)
> +{
> + struct iw_node_attr *node_attr;
> + u8 weight;
> + u8 __rcu *table;
> +
> + node_attr = container_of(attr, struct iw_node_attr, kobj_attr);
> +
> + rcu_read_lock();
> + table = rcu_dereference(iw_table);
> + weight = table ? table[node_attr->nid] : 1;
> + rcu_read_unlock();
> +
> + return sysfs_emit(buf, "%d\n", weight);
> +}
> +
> +static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct iw_node_attr *node_attr;
> + u8 __rcu *new;
> + u8 __rcu *old;
> + u8 weight = 0;
> +
> + node_attr = container_of(attr, struct iw_node_attr, kobj_attr);
> + if (count == 0 || sysfs_streq(buf, ""))
> + weight = 0;
> + else if (kstrtou8(buf, 0, &weight))
> + return -EINVAL;
> +
> + /*
> + * The default weight is 1 (for now), when the kernel-internal
> + * default weight array is implemented, this should be updated to
> + * collect the system-default weight of the node if the user passes 0.
> + */
> + if (!weight)
> + weight = 1;
>From functionality point of view, it's OK to set "weight = 1" here now.
But when we add system default weight table in the future, we need to
use "weight = 0". Otherwise, we cannot distinguish whether the default
value have been customized via sysfs. So, I suggest to use that rule.
> +
> + /* We only need to allocate up to the number of possible nodes */
This comment appears not necessary.
> + new = kmalloc(nr_node_ids, GFP_KERNEL);
> + if (!new)
> + return -ENOMEM;
> +
> + mutex_lock(&iw_table_lock);
> + old = rcu_dereference_protected(iw_table,
> + lockdep_is_held(&iw_table_lock));
> + if (old)
> + memcpy(new, old, nr_node_ids);
> + else
> + memset(new, 1, nr_node_ids);
With similar reason as above ("From functionality..."), I suggest to set
"0" here.
> + new[node_attr->nid] = weight;
> + rcu_assign_pointer(iw_table, new);
> + mutex_unlock(&iw_table_lock);
> + synchronize_rcu();
> + kfree(old);
> + return count;
> +}
> +
> +static struct iw_node_attr *node_attrs[MAX_NUMNODES];
node_attrs[] can be allocated dynamically too. Just a suggestion.
> +
> +static void sysfs_wi_node_release(struct iw_node_attr *node_attr,
> + struct kobject *parent)
> +{
> + if (!node_attr)
> + return;
> + sysfs_remove_file(parent, &node_attr->kobj_attr.attr);
> + kfree(node_attr->kobj_attr.attr.name);
> + kfree(node_attr);
> +}
> +
> +static void sysfs_wi_release(struct kobject *wi_kobj)
> +{
> + int i;
> +
> + for (i = 0; i < MAX_NUMNODES; i++)
Nitpick, nr_node_ids should be OK here.
> + sysfs_wi_node_release(node_attrs[i], wi_kobj);
> + kobject_put(wi_kobj);
> +}
> +
> +static const struct kobj_type wi_ktype = {
> + .sysfs_ops = &kobj_sysfs_ops,
> + .release = sysfs_wi_release,
> +};
> +
> +static int add_weight_node(int nid, struct kobject *wi_kobj)
> +{
> + struct iw_node_attr *node_attr;
> + char *name;
> +
> + node_attr = kzalloc(sizeof(*node_attr), GFP_KERNEL);
> + if (!node_attr)
> + return -ENOMEM;
> +
> + name = kasprintf(GFP_KERNEL, "node%d", nid);
> + if (!name) {
> + kfree(node_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;
> +
> + if (sysfs_create_file(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;
> + }
> +
> + node_attrs[nid] = node_attr;
> + return 0;
> +}
> +
> +static int add_weighted_interleave_group(struct kobject *root_kobj)
> +{
> + struct kobject *wi_kobj;
> + int nid, err;
> +
> + wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
> + if (!wi_kobj)
> + return -ENOMEM;
> +
> + err = kobject_init_and_add(wi_kobj, &wi_ktype, root_kobj,
> + "weighted_interleave");
> + if (err) {
> + kfree(wi_kobj);
> + return err;
> + }
> +
> + memset(node_attrs, 0, sizeof(node_attrs));
> + for_each_node_state(nid, N_POSSIBLE) {
> + err = add_weight_node(nid, wi_kobj);
> + if (err) {
> + pr_err("failed to add sysfs [node%d]\n", nid);
> + break;
> + }
> + }
> + if (err)
> + kobject_put(wi_kobj);
> + return 0;
> +}
> +
> +static void mempolicy_kobj_release(struct kobject *kobj)
> +{
> + u8 __rcu *old;
> +
> + mutex_lock(&iw_table_lock);
> + old = rcu_dereference_protected(iw_table,
> + lockdep_is_held(&iw_table_lock));
> + rcu_assign_pointer(iw_table, NULL);
> + mutex_unlock(&iw_table_lock);
> + synchronize_rcu();
> + /* Never free the default table, it's always in use */
Obsolete comment?
> + kfree(old);
It appears unnecessary to free iw_table in error path. But this isn't a
big deal because error path will almost never be executed in practice.
> + kfree(kobj);
> +}
> +
> +static const struct kobj_type mempolicy_ktype = {
> + .release = mempolicy_kobj_release
> +};
> +
> +static struct kobject *mempolicy_kobj;
> +static int __init mempolicy_sysfs_init(void)
> +{
> + int err;
> + struct kobject *mempolicy_kobj;
This overrides the global "mempolicy_kobj" defined before function. But
I don't think we need the global definition.
> +
> + /* A NULL iw_table is interpreted by interleave logic as "all 1s" */
As I suggested above, it will be "all 0s", that is, use default weight.
> + iw_table = NULL;
The default value is NULL already, it appears unnecessary to do this.
> + mempolicy_kobj = kzalloc(sizeof(*mempolicy_kobj), GFP_KERNEL);
> + if (!mempolicy_kobj) {
> + pr_err("failed to add mempolicy kobject to the system\n");
> + return -ENOMEM;
> + }
> + err = kobject_init_and_add(mempolicy_kobj, &mempolicy_ktype, mm_kobj,
> + "mempolicy");
> + if (err) {
> + kfree(mempolicy_kobj);
> + return err;
> + }
> +
> + err = add_weighted_interleave_group(mempolicy_kobj);
> +
> + if (err) {
> + kobject_put(mempolicy_kobj);
> + return err;
> + }
> +
> + return err;
> +}
> +
> +static void __exit mempolicy_exit(void)
> +{
> + if (mempolicy_kobj)
> + kobject_put(mempolicy_kobj);
> +}
> +
> +#else
> +static int __init mempolicy_sysfs_init(void)
> +{
> + /* A NULL iw_table is interpreted by interleave logic as "all 1s" */
> + iw_table = NULL;
> + return 0;
> +}
> +
> +static void __exit mempolicy_exit(void) { }
> +#endif /* CONFIG_SYSFS */
> +late_initcall(mempolicy_sysfs_init);
> +module_exit(mempolicy_exit);
mempolicy.c will not be compiled as module, so we don't need
module_exit().
--
Best Regards,
Huang, Ying
