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Message-ID: <uxqkbmqbvcvx6wc3g2h6vhkutv5flrq6rslwdfs7pa6kknupwh@a245pbtfqfgj>
Date: Thu, 7 Dec 2023 13:56:07 -0800
From: Davidlohr Bueso <dave@...olabs.net>
To: Gregory Price <gourry.memverge@...il.com>
Cc: linux-mm@...ck.org, jgroves@...ron.com, ravis.opensrc@...ron.com,
sthanneeru@...ron.com, emirakhur@...ron.com, Hasan.Maruf@....com,
linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
arnd@...db.de, tglx@...utronix.de, luto@...nel.org,
mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
x86@...nel.org, hpa@...or.com, mhocko@...nel.org, tj@...nel.org,
ying.huang@...el.com, gregory.price@...verge.com, corbet@....net,
rakie.kim@...com, hyeongtak.ji@...com, honggyu.kim@...com,
vtavarespetr@...ron.com, peterz@...radead.org
Subject: Re: [RFC PATCH 01/11] mm/mempolicy: implement the sysfs-based
weighted_interleave interface
On Wed, 06 Dec 2023, Gregory Price wrote:
>Signed-off-by: Rakie Kim <rakie.kim@...com>
>Signed-off-by: Honggyu Kim <honggyu.kim@...com>
>Co-developed-by: Gregory Price <gregory.price@...verge.com>
>Signed-off-by: Gregory Price <gregory.price@...verge.com>
>Co-developed-by: Hyeongtak Ji <hyeongtak.ji@...com>
>Signed-off-by: Hyeongtak Ji <hyeongtak.ji@...com>
fyi Rakie's tag needs to be last, per the From.
...
>+What: /sys/kernel/mm/mempolicy/weighted_interleave/
>+Date: December 2023
>+Contact: Linux memory management mailing list <linux-mm@...ck.org>
>+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@...ck.org>
>+Description: Configuration interface for accesses initiated from nodeN
>+
>+ The directory to configure access initiator weights for nodeN.
>+
>+ Possible numa nodes which have not been marked as a CPU node
>+ at boot will not have a nodeN directory made for them at boot.
This could be better rephrased without the negation. ie:
"Only numa nodes with CPUs (compute) will have a nodeN directory."
>+ Hotplug for CPU nodes is not supported.
Can this even happen? Hot-adding a previously offlined CPU won't change/add a
new numa node. So just rm the line altogether?
>+
>+What: /sys/kernel/mm/mempolicy/weighted_interleave/nodeN/nodeM
>+ /sys/kernel/mm/mempolicy/weighted_interleave/nodeN/nodeM/weight
>+Date: December 2023
>+Contact: Linux memory management mailing list <linux-mm@...ck.org>
>+Description: Configuration interface for target nodes accessed from nodeNN
>+
>+ The interleave weight for a memory node (M) from initiating
>+ node (N). These weights are utilized by processes which have set
>+ the 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.
>+
>+ If the weight of 0 is desired, the appropriate way to do this is
>+ by removing the node from the weighted interleave nodemask.
>+
>+ Minimum weight: 1
>+ Maximum weight: 255
>diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>index 10a590ee1c89..ce332b5e7a03 100644
>--- a/mm/mempolicy.c
>+++ b/mm/mempolicy.c
>@@ -131,6 +131,11 @@ static struct mempolicy default_policy = {
>
> static struct mempolicy preferred_node_policy[MAX_NUMNODES];
>
>+struct interleave_weight_table {
>+ unsigned char weights[MAX_NUMNODES];
>+};
>+static struct interleave_weight_table *iw_table;
>+
> /**
> * numa_nearest_node - Find nearest node by state
> * @node: Node id to start the search
>@@ -3067,3 +3072,224 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
> p += scnprintf(p, buffer + maxlen - p, ":%*pbl",
> nodemask_pr_args(&nodes));
> }
>+
>+struct iw_node_info {
>+ struct kobject kobj;
>+ int src;
>+ int dst;
>+};
>+
>+static ssize_t node_weight_show(struct kobject *kobj,
>+ struct kobj_attribute *attr, char *buf)
>+{
>+ struct iw_node_info *node_info = container_of(kobj, struct iw_node_info,
>+ kobj);
>+ return sysfs_emit(buf, "%d\n",
>+ iw_table[node_info->src].weights[node_info->dst]);
>+}
>+
>+static ssize_t node_weight_store(struct kobject *kobj,
>+ struct kobj_attribute *attr,
>+ const char *buf, size_t count)
>+{
>+ unsigned char weight = 0;
>+ struct iw_node_info *node_info = NULL;
>+
>+ node_info = container_of(kobj, struct iw_node_info, kobj);
>+
>+ if (kstrtou8(buf, 0, &weight) || !weight)
>+ return -EINVAL;
>+
>+ iw_table[node_info->src].weights[node_info->dst] = weight;
>+
>+ return count;
>+}
iw_table will need some (basic) form of serialization.
...
>+static int __init mempolicy_sysfs_init(void)
>+{
>+ int err, nid;
>+ int cpunodes = 0;
>+ struct kobject *root_kobj;
>+
>+ for_each_node_state(nid, N_CPU)
>+ cpunodes += 1;
>+ iw_table = kmalloc_array(cpunodes, sizeof(*iw_table), GFP_KERNEL);
>+ if (!iw_table) {
>+ pr_err("failed to create interleave weight table\n");
>+ err = -ENOMEM;
>+ goto fail_obj;
No ref here yet, just return -ENOMEM.
>+ }
>+ memset(iw_table, 1, cpunodes * sizeof(*iw_table));
>+
>+ root_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
>+ if (!root_kobj)
>+ return -ENOMEM;
>+
>+ kobject_init(root_kobj, &mempolicy_kobj_ktype);
>+ err = kobject_add(root_kobj, mm_kobj, "mempolicy");
>+ if (err) {
>+ pr_err("failed to add kobject to the system\n");
>+ goto fail_obj;
>+ }
>+
>+ err = sysfs_create_group(root_kobj, &mempolicy_attr_group);
>+ if (err) {
>+ pr_err("failed to register mempolicy group\n");
>+ goto fail_obj;
>+ }
>+
>+ err = add_weighted_interleave_group(root_kobj);
>+fail_obj:
>+ if (err)
>+ kobject_put(root_kobj);
>+ return err;
>+
>+}
>+late_initcall(mempolicy_sysfs_init);
>--
>2.39.1
>
>
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