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 sysfs is disabled in the config, the global interleave weights
> will default to "1" for all nodes.
>
> 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 | 22 +++
> mm/mempolicy.c | 156 ++++++++++++++++++
> 3 files changed, 182 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..aa27fdf08c19
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave
> @@ -0,0 +1,22 @@
> +What: /sys/kernel/mm/mempolicy/weighted_interleave/
> +Date: December 2023
> +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
> + MPOL_WEIGHTED_INTERLEAVE and have opted into global weights by
> + omitting a task-local weight array.
> +
> + These weights only affect new allocations, and changes at runtime
> + will not cause migrations on already allocated pages.
> +
> + Writing an empty string resets the weight value to 1.
I still think that it's a good idea to provide some better default
weight value with HMAT or CDAT if available. So, better not to make "1"
as part of ABI?
> +
> + Minimum weight: 1
Can weight be "0"? Do we need a way to specify that a node don't want
to participate weighted interleave?
> + Maximum weight: 255
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 10a590ee1c89..0e77633b07a5 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -131,6 +131,8 @@ static struct mempolicy default_policy = {
>
> static struct mempolicy preferred_node_policy[MAX_NUMNODES];
>
> +static char iw_table[MAX_NUMNODES];
> +
It's kind of obscure whether "char" is "signed" or "unsigned". Given
the max weight is 255 above, it's better to use "u8"?
And, we may need a way to specify whether the weight has been overridden
by the user. A special value (such as 255) can be used for that. If
so, the maximum weight should be 254 instead of 255. As a user space
interface, is it better to use 100 as the maximum value?
> /**
> * numa_nearest_node - Find nearest node by state
> * @node: Node id to start the search
> @@ -3067,3 +3069,157 @@ 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;
> +
> + node_attr = container_of(attr, struct iw_node_attr, kobj_attr);
> + return sysfs_emit(buf, "%d\n", iw_table[node_attr->nid]);
> +}
> +
> +static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct iw_node_attr *node_attr;
> + unsigned char weight = 0;
> +
> + node_attr = container_of(attr, struct iw_node_attr, kobj_attr);
> + /* If no input, set default weight to 1 */
> + if (count == 0 || sysfs_streq(buf, ""))
> + weight = 1;
> + else if (kstrtou8(buf, 0, &weight) || !weight)
> + return -EINVAL;
> +
> + iw_table[node_attr->nid] = weight;
kstrtou8(), "unsigned char weight", "char iw_table[]" isn't completely
consistent. It's better to make them consistent?
> + return count;
> +}
> +
> +static struct iw_node_attr *node_attrs[MAX_NUMNODES];
> +
> +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_mempolicy_release(struct kobject *mempolicy_kobj)
> +{
> + int i;
> +
> + for (i = 0; i < MAX_NUMNODES; i++)
> + sysfs_wi_node_release(node_attrs[i], mempolicy_kobj);
IIUC, if this is called in error path (such as, in
add_weighted_interleave_group()), some node_attrs[] element may be
"NULL"?
> + kobject_put(mempolicy_kobj);
> +}
> +
> +static const struct kobj_type mempolicy_ktype = {
> + .sysfs_ops = &kobj_sysfs_ops,
> + .release = sysfs_mempolicy_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, &mempolicy_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 int __init mempolicy_sysfs_init(void)
> +{
> + int err;
> + struct kobject *root_kobj;
> +
> + memset(&iw_table, 1, sizeof(iw_table));
> +
> + root_kobj = kobject_create_and_add("mempolicy", mm_kobj);
> + if (!root_kobj) {
> + pr_err("failed to add mempolicy kobject to the system\n");
> + return -ENOMEM;
> + }
> +
> + err = add_weighted_interleave_group(root_kobj);
> +
> + if (err)
> + kobject_put(root_kobj);
> + return err;
> +
> +}
> +#else
> +static int __init mempolicy_sysfs_init(void)
> +{
> + /*
> + * if sysfs is not enabled MPOL_WEIGHTED_INTERLEAVE defaults to
> + * MPOL_INTERLEAVE behavior, but is still defined separately to
> + * allow task-local weighted interleave to operate as intended.
> + */
> + memset(&iw_table, 1, sizeof(iw_table));
> + return 0;
> +}
> +#endif /* CONFIG_SYSFS */
> +late_initcall(mempolicy_sysfs_init);
--
Best Regards,
Huang, Ying
