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Message-ID: <20250408135202.3001047-1-joshua.hahnjy@gmail.com>
Date: Tue, 8 Apr 2025 06:52:01 -0700
From: Joshua Hahn <joshua.hahnjy@...il.com>
To: Rakie Kim <rakie.kim@...com>
Cc: akpm@...ux-foundation.org,
gourry@...rry.net,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
linux-cxl@...r.kernel.org,
joshua.hahnjy@...il.com,
dan.j.williams@...el.com,
ying.huang@...ux.alibaba.com,
david@...hat.com,
Jonathan.Cameron@...wei.com,
osalvador@...e.de,
kernel_team@...ynix.com,
honggyu.kim@...com,
yunjeong.mun@...com
Subject: Re: [PATCH v7 3/3] mm/mempolicy: Support memory hotplug in weighted interleave
On Tue, 8 Apr 2025 16:32:42 +0900 Rakie Kim <rakie.kim@...com> wrote:
Hi Rakie,
Looks good to me as well : -) Thank you for working on this!
Reviewed-by: Joshua Hahn <joshua.hahnjy@...il.com>
> 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@...com>
> Signed-off-by: Honggyu Kim <honggyu.kim@...com>
> Signed-off-by: Yunjeong Mun <yunjeong.mun@...com>
> Reviewed-by: Oscar Salvador <osalvador@...e.de>
> ---
> mm/mempolicy.c | 106 ++++++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 83 insertions(+), 23 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 988575f29c53..9aa884107f4c 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"
>
> @@ -3421,6 +3422,7 @@ struct iw_node_attr {
>
> struct sysfs_wi_group {
> struct kobject wi_kobj;
> + struct mutex kobj_lock;
> struct iw_node_attr *nattrs[];
> };
>
> @@ -3470,13 +3472,24 @@ 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)
> @@ -3495,35 +3508,77 @@ 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)
> + return NOTIFY_OK;
> +
> + switch(action) {
> + case MEM_ONLINE:
> + err = sysfs_wi_node_add(nid);
> + if (err)
> + pr_err("failed to add sysfs [node%d]\n", nid);
> + break;
> + case MEM_OFFLINE:
> + sysfs_wi_node_delete(nid);
> + break;
> + }
> +
> + return NOTIFY_OK;
> }
>
> static int __init add_weighted_interleave_group(struct kobject *mempolicy_kobj)
> @@ -3534,13 +3589,17 @@ static int __init 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_put_kobj;
>
> - 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);
> @@ -3548,6 +3607,7 @@ static int __init add_weighted_interleave_group(struct kobject *mempolicy_kobj)
> }
> }
>
> + hotplug_memory_notifier(wi_node_notifier, DEFAULT_CALLBACK_PRI);
> return 0;
>
> err_del_kobj:
> --
> 2.34.1
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