@@ -20,6 +20,34 @@ Description: Weight configuration interface for nodeN
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.
+ Writing invalid values (i.e. any values not in [1,255],
+ empty string, ...) will return -EINVAL.
+
+ Changing the weight to a valid value will automatically
+ update the system to manual mode as well.
+
+What: /sys/kernel/mm/mempolicy/weighted_interleave/auto
+Date: January 2025
+Contact: Linux memory management mailing list <linux-mm@kvack.org>
+Description: Auto-weighting configuration interface
+
+ Configuration mode for weighted interleave. A 'Y' indicates
+ that the system is in auto mode, and a 'N' indicates that
+ the system is in manual mode. All other values are invalid.
+
+ In auto mode, all node weights are re-calculated and overwritten
+ (visible via the nodeN interfaces) whenever new bandwidth data
+ is made available during either boot or hotplug events.
+
+ In manual mode, node weights can only be updated by the user.
+ If a node is hotplugged while the user is in manual mode,
+ the node will have a default weight of 1.
+
+ Modes can be changed by writing Y, N, 1, or 0 to the interface.
+ All other strings will be ignored, and -EINVAL will be returned.
+ If Y or 1 is written to the interface but the recalculation or
+ updates fail at any point (-ENOMEM or -ENODEV), then the mode
+ will remain in manual mode.
+
+ Writing a new weight to a node directly via the nodeN interface
+ will also automatically update the system to manual mode.
@@ -20,6 +20,7 @@
#include <linux/list_sort.h>
#include <linux/memregion.h>
#include <linux/memory.h>
+#include <linux/mempolicy.h>
#include <linux/mutex.h>
#include <linux/node.h>
#include <linux/sysfs.h>
@@ -7,6 +7,7 @@
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/memory.h>
+#include <linux/mempolicy.h>
#include <linux/vmstat.h>
#include <linux/notifier.h>
#include <linux/node.h>
@@ -214,6 +215,12 @@ void node_set_perf_attrs(unsigned int nid, struct access_coordinate *coord,
break;
}
}
+
+ /* When setting CPU access coordinates, update mempolicy */
+ if (access == ACCESS_COORDINATE_CPU) {
+ if (mempolicy_set_node_perf(nid, coord))
+ pr_info("failed to set node%d mempolicy attrs\n", nid);
+ }
}
EXPORT_SYMBOL_GPL(node_set_perf_attrs);
@@ -11,6 +11,7 @@
#include <linux/slab.h>
#include <linux/rbtree.h>
#include <linux/spinlock.h>
+#include <linux/node.h>
#include <linux/nodemask.h>
#include <linux/pagemap.h>
#include <uapi/linux/mempolicy.h>
@@ -178,6 +179,9 @@ static inline bool mpol_is_preferred_many(struct mempolicy *pol)
extern bool apply_policy_zone(struct mempolicy *policy, enum zone_type zone);
+extern int mempolicy_set_node_perf(unsigned int node,
+ struct access_coordinate *coords);
+
#else
struct mempolicy {};
@@ -109,6 +109,7 @@
#include <linux/mmu_notifier.h>
#include <linux/printk.h>
#include <linux/swapops.h>
+#include <linux/gcd.h>
#include <asm/tlbflush.h>
#include <asm/tlb.h>
@@ -138,16 +139,18 @@ static struct mempolicy default_policy = {
static struct mempolicy preferred_node_policy[MAX_NUMNODES];
+static uint64_t *node_bw_table;
+
/*
- * iw_table is the sysfs-set interleave weight table, a value of 0 denotes
- * system-default value should be used. A NULL iw_table also denotes that
- * system-default values should be used. Until the system-default table
- * is implemented, the system-default is always 1.
- *
+ * iw_table is the interleave weight table.
+ * If bandwiddth data is available and the user is in auto mode, the table
+ * is populated with default values in [1,255].
* iw_table is RCU protected
*/
static u8 __rcu *iw_table;
static DEFINE_MUTEX(iw_table_lock);
+static const int weightiness = 32;
+static bool weighted_interleave_auto = true;
static u8 get_il_weight(int node)
{
@@ -156,14 +159,113 @@ static u8 get_il_weight(int node)
rcu_read_lock();
table = rcu_dereference(iw_table);
- /* if no iw_table, use system default */
weight = table ? table[node] : 1;
- /* if value in iw_table is 0, use system default */
- weight = weight ? weight : 1;
rcu_read_unlock();
return weight;
}
+/*
+ * Convert bandwidth values into weighted interleave weights.
+ * Call with iw_table_lock.
+ */
+static void reduce_interleave_weights(uint64_t *bw, u8 *new_iw)
+{
+ uint64_t ttl_bw = 0, ttl_iw = 0, scaling_factor = 1, iw_gcd = 1;
+ unsigned int i = 0;
+
+ /* Recalculate the bandwidth distribution given the new info */
+ for (i = 0; i < nr_node_ids; i++)
+ ttl_bw += bw[i];
+
+ /* If node is not set or has < 1% of total bw, use minimum value of 1 */
+ for (i = 0; i < nr_node_ids; i++) {
+ if (bw[i]) {
+ scaling_factor = 100 * bw[i];
+ new_iw[i] = max(scaling_factor / ttl_bw, 1);
+ } else {
+ new_iw[i] = 1;
+ }
+ ttl_iw += new_iw[i];
+ }
+
+ /*
+ * Scale each node's share of the total bandwidth from percentages
+ * to whole numbers in the range [1, weightiness]
+ */
+ for (i = 0; i < nr_node_ids; i++) {
+ scaling_factor = weightiness * new_iw[i];
+ new_iw[i] = max(scaling_factor / ttl_iw, 1);
+ if (i == 0)
+ iw_gcd = new_iw[0];
+ iw_gcd = gcd(iw_gcd, new_iw[i]);
+ }
+
+ /* 1:2 is strictly better than 16:32. Reduce by the weights' GCD. */
+ for (i = 0; i < nr_node_ids; i++)
+ new_iw[i] /= iw_gcd;
+}
+
+int mempolicy_set_node_perf(unsigned int node, struct access_coordinate *coords)
+{
+ uint64_t *old_bw, *new_bw;
+ uint64_t bw_val;
+ u8 *old_iw, *new_iw;
+
+ /*
+ * Bandwidths above this limit cause rounding errors when reducing
+ * weights. This value is ~16 exabytes, which is unreasonable anyways.
+ */
+ bw_val = min(coords->read_bandwidth, coords->write_bandwidth);
+ if (bw_val > (U64_MAX / 10))
+ return -EINVAL;
+
+ new_bw = kcalloc(nr_node_ids, sizeof(uint64_t), GFP_KERNEL);
+ if (!new_bw)
+ return -ENOMEM;
+
+ new_iw = kcalloc(nr_node_ids, sizeof(u8), GFP_KERNEL);
+ if (!new_iw) {
+ kfree(new_bw);
+ return -ENOMEM;
+ }
+
+ /*
+ * Update bandwidth info, even in manual mode. That way, when switching
+ * to auto mode in the future, iw_table can be overwritten using
+ * accurate bw data.
+ */
+ mutex_lock(&iw_table_lock);
+ old_bw = node_bw_table;
+ old_iw = rcu_dereference_protected(iw_table,
+ lockdep_is_held(&iw_table_lock));
+
+ if (old_bw)
+ memcpy(new_bw, old_bw, nr_node_ids*sizeof(uint64_t));
+ new_bw[node] = bw_val;
+ node_bw_table = new_bw;
+
+ if (weighted_interleave_auto) {
+ reduce_interleave_weights(new_bw, new_iw);
+ } else if (old_iw) {
+ /*
+ * The first time mempolicy_set_node_perf is called, old_iw
+ * (iw_table) is null. If that is the case, assign a zeroed
+ * table to it. Otherwise, free the newly allocated iw_table.
+ */
+ mutex_unlock(&iw_table_lock);
+ kfree(new_iw);
+ kfree(old_bw);
+ return 0;
+ }
+
+ rcu_assign_pointer(iw_table, new_iw);
+ mutex_unlock(&iw_table_lock);
+ synchronize_rcu();
+ kfree(old_iw);
+ kfree(old_bw);
+ return 0;
+}
+
/**
* numa_nearest_node - Find nearest node by state
* @node: Node id to start the search
@@ -1998,10 +2100,7 @@ static unsigned int weighted_interleave_nid(struct mempolicy *pol, pgoff_t ilx)
table = rcu_dereference(iw_table);
/* calculate the total weight */
for_each_node_mask(nid, nodemask) {
- /* detect system default usage */
- weight = table ? table[nid] : 1;
- weight = weight ? weight : 1;
- weight_total += weight;
+ weight_total += table ? table[nid] : 1;
}
/* Calculate the node offset based on totals */
@@ -2010,7 +2109,6 @@ static unsigned int weighted_interleave_nid(struct mempolicy *pol, pgoff_t ilx)
while (target) {
/* detect system default usage */
weight = table ? table[nid] : 1;
- weight = weight ? weight : 1;
if (target < weight)
break;
target -= weight;
@@ -3394,7 +3492,7 @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
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))
+ else if (kstrtou8(buf, 0, &weight) || weight == 0)
return -EINVAL;
new = kzalloc(nr_node_ids, GFP_KERNEL);
@@ -3411,11 +3509,68 @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
mutex_unlock(&iw_table_lock);
synchronize_rcu();
kfree(old);
+ weighted_interleave_auto = false;
return count;
}
static struct iw_node_attr **node_attrs;
+static ssize_t weighted_interleave_mode_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ if (weighted_interleave_auto)
+ return sysfs_emit(buf, "Y\n");
+ else
+ return sysfs_emit(buf, "N\n");
+}
+
+static ssize_t weighted_interleave_mode_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf, size_t count)
+{
+ uint64_t *bw;
+ u8 *old_iw, *new_iw;
+
+ if (count == 0)
+ return -EINVAL;
+
+ if (sysfs_streq(buf, "N") || sysfs_streq(buf, "0")) {
+ weighted_interleave_auto = false;
+ return count;
+ } else if (!sysfs_streq(buf, "Y") && !sysfs_streq(buf, "1")) {
+ return -EINVAL;
+ }
+
+ new_iw = kcalloc(nr_node_ids, sizeof(u8), GFP_KERNEL);
+ if (!new_iw)
+ return -ENOMEM;
+
+ mutex_lock(&iw_table_lock);
+ bw = node_bw_table;
+
+ if (!bw) {
+ mutex_unlock(&iw_table_lock);
+ kfree(new_iw);
+ return -ENODEV;
+ }
+
+ old_iw = rcu_dereference_protected(iw_table,
+ lockdep_is_held(&iw_table_lock));
+
+ reduce_interleave_weights(bw, new_iw);
+ rcu_assign_pointer(iw_table, new_iw);
+ mutex_unlock(&iw_table_lock);
+
+ synchronize_rcu();
+ kfree(old_iw);
+
+ weighted_interleave_auto = true;
+ return count;
+}
+
+static struct kobj_attribute wi_attr =
+ __ATTR(auto, 0664, weighted_interleave_mode_show,
+ weighted_interleave_mode_store);
+
static void sysfs_wi_node_release(struct iw_node_attr *node_attr,
struct kobject *parent)
{
@@ -3432,6 +3587,7 @@ static void sysfs_wi_release(struct kobject *wi_kobj)
for (i = 0; i < nr_node_ids; i++)
sysfs_wi_node_release(node_attrs[i], wi_kobj);
+
kobject_put(wi_kobj);
}
@@ -3473,6 +3629,15 @@ static int add_weight_node(int nid, struct kobject *wi_kobj)
return 0;
}
+static struct attribute *wi_default_attrs[] = {
+ &wi_attr.attr,
+ NULL
+};
+
+static const struct attribute_group wi_attr_group = {
+ .attrs = wi_default_attrs,
+};
+
static int add_weighted_interleave_group(struct kobject *root_kobj)
{
struct kobject *wi_kobj;
@@ -3489,6 +3654,13 @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
return err;
}
+ err = sysfs_create_group(wi_kobj, &wi_attr_group);
+ if (err) {
+ pr_err("failed to add sysfs [auto]\n");
+ kobject_put(wi_kobj);
+ return err;
+ }
+
for_each_node_state(nid, N_POSSIBLE) {
err = add_weight_node(nid, wi_kobj);
if (err) {