[PATCH v3 11/11] mm/mempolicy: extend set_mempolicy2 and mbind2 to support weighted interleave

Gregory Price
2023-12-13T22:41:48Z

Extend set_mempolicy2 and mbind2 to support weighted interleave, and
demonstrate the extensibility of the mpol_args structure.

To support weighted interleave we add interleave weight fields to the
following structures:

Kernel Internal: (include/linux/mempolicy.h)
struct mempolicy {
/* task-local weights to apply to weighted interleave */
unsigned char weights[MAX_NUMNODES];
}
struct mempolicy_args {
/* Optional: interleave weights for MPOL_WEIGHTED_INTERLEAVE */
unsigned char *il_weights; /* of size MAX_NUMNODES */
}

UAPI: (/include/uapi/linux/mempolicy.h)
struct mpol_args {
/* Optional: interleave weights for MPOL_WEIGHTED_INTERLEAVE */
unsigned char *il_weights; /* of size pol_max_nodes */
}

The task-local weights are a single, one-dimensional array of weights
that apply to all possible nodes on the system. If a node is set in
the mempolicy nodemask, the weight in `il_weights` must be >= 1,
otherwise set_mempolicy2() will return -EINVAL. If a node is not
set in pol_nodemask, the weight will default to `1` in the task policy.

The default value of `1` is required to handle the situation where a
task migrates to a set of nodes for which weights were not set (up to
and including the local numa node). For example, a migrated task whose
nodemask changes entirely will have all its weights defaulted back
to `1`, or if the nodemask changes to include a mix of nodes that
were not previously accounted for - the weighted interleave may be
suboptimal.

If migrations are expected, a task should prefer not to use task-local
interleave weights, and instead utilize the global settings for natural
re-weighting on migration.

To support global vs local weighting, we add the kernel-internal flag:
MPOL_F_GWEIGHT (1 << 5) /* Utilize global weights */

This flag is set when il_weights is omitted by set_mempolicy2(), or
when MPOL_WEIGHTED_INTERLEAVE is set by set_mempolicy(). This internal
mode_flag dictates whether global weights or task-local weights are
utilized by the the various weighted interleave functions:

* weighted_interleave_nodes
* weighted_interleave_nid
* alloc_pages_bulk_array_weighted_interleave

if (pol->flags & MPOL_F_GWEIGHT)
pol_weights = iw_table;
else
pol_weights = pol->wil.weights;

To simplify creations and duplication of mempolicies, the weights are
added as a structure directly within mempolicy. This allows the
existing logic in __mpol_dup to copy the weights without additional
allocations:

if (old == current->mempolicy) {
task_lock(current);
*new = *old;
task_unlock(current);
} else
*new = *old

Suggested-by: Rakie Kim <rakie.kim@sk.com>
Suggested-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
Suggested-by: Honggyu Kim <honggyu.kim@sk.com>
Suggested-by: Vinicius Tavares Petrucci <vtavarespetr@micron.com>
Signed-off-by: Gregory Price <gregory.price@memverge.com>
Co-developed-by: Rakie Kim <rakie.kim@sk.com>
Signed-off-by: Rakie Kim <rakie.kim@sk.com>
Co-developed-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
Signed-off-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
Co-developed-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Co-developed-by: Vinicius Tavares Petrucci <vtavarespetr@micron.com>
Signed-off-by: Vinicius Tavares Petrucci <vtavarespetr@micron.com>
---
.../admin-guide/mm/numa_memory_policy.rst | 10 ++
include/linux/mempolicy.h | 2 +
include/uapi/linux/mempolicy.h | 2 +
mm/mempolicy.c | 129 +++++++++++++++++-
4 files changed, 139 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/mm/numa_memory_policy.rst b/Documentation/admin-guide/mm/numa_memory_policy.rst
index 99e1f732cade..0e91efe9e769 100644
--- a/Documentation/admin-guide/mm/numa_memory_policy.rst
+++ b/Documentation/admin-guide/mm/numa_memory_policy.rst
@@ -254,6 +254,8 @@ MPOL_WEIGHTED_INTERLEAVE
This mode operates the same as MPOL_INTERLEAVE, except that
interleaving behavior is executed based on weights set in
/sys/kernel/mm/mempolicy/weighted_interleave/
+ when configured to utilize global weights, or based on task-local
+ weights configured with set_mempolicy2(2) or mbind2(2).

Weighted interleave allocations pages on nodes according to
their weight. For example if nodes [0,1] are weighted [5,2]
@@ -261,6 +263,13 @@ MPOL_WEIGHTED_INTERLEAVE
2 pages allocated on node1. This can better distribute data
according to bandwidth on heterogeneous memory systems.

+ When utilizing task-local weights, weights are not rebalanced
+ in the event of a task migration. If a weight has not been
+ explicitly set for a node set in the new nodemask, the
+ value of that weight defaults to "1". For this reason, if
+ migrations are expected or possible, users should consider
+ utilizing global interleave weights.
+
NUMA memory policy supports the following optional mode flags:

MPOL_F_STATIC_NODES
@@ -514,6 +523,7 @@ Extended Mempolicy Arguments::
__u16 mode_flags;
__s32 home_node; /* mbind2: policy home node */
__aligned_u64 pol_nodes; /* nodemask pointer */
+ __aligned_u64 il_weights; /* u8 buf of size pol_maxnodes */
__u64 pol_maxnodes;
__s32 policy_node; /* get_mempolicy2: policy node information */
};
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index aeac19dfc2b6..387c5c418a66 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -58,6 +58,7 @@ struct mempolicy {
/* Weighted interleave settings */
struct {
unsigned char cur_weight;
+ unsigned char weights[MAX_NUMNODES];
} wil;
};

@@ -70,6 +71,7 @@ struct mempolicy_args {
unsigned short mode_flags; /* policy mode flags */
int home_node; /* mbind: use MPOL_MF_HOME_NODE */
nodemask_t *policy_nodes; /* get/set/mbind */
+ unsigned char *il_weights; /* for mode MPOL_WEIGHTED_INTERLEAVE */
int policy_node; /* get: policy node information */
};

diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h
index ec1402dae35b..16fedf966166 100644
--- a/include/uapi/linux/mempolicy.h
+++ b/include/uapi/linux/mempolicy.h
@@ -33,6 +33,7 @@ struct mpol_args {
__u16 mode_flags;
__s32 home_node; /* mbind2: policy home node */
__aligned_u64 pol_nodes;
+ __aligned_u64 il_weights; /* size: pol_maxnodes * sizeof(char) */
__u64 pol_maxnodes;
__s32 policy_node; /* get_mempolicy: policy node info */
};
@@ -75,6 +76,7 @@ struct mpol_args {
#define MPOL_F_SHARED (1 << 0) /* identify shared policies */
#define MPOL_F_MOF (1 << 3) /* this policy wants migrate on fault */
#define MPOL_F_MORON (1 << 4) /* Migrate On protnone Reference On Node */
+#define MPOL_F_GWEIGHT (1 << 5) /* Utilize global weights */

/*
* These bit locations are exposed in the vm.zone_reclaim_mode sysctl
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 68ea8e177217..15d047098429 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -271,6 +271,7 @@ static struct mempolicy *mpol_new(struct mempolicy_args *args)
unsigned short mode = args->mode;
unsigned short flags = args->mode_flags;
nodemask_t *nodes = args->policy_nodes;
+ int node;

if (mode == MPOL_DEFAULT) {
if (nodes && !nodes_empty(*nodes))
@@ -297,6 +298,19 @@ static struct mempolicy *mpol_new(struct mempolicy_args *args)
(flags & MPOL_F_STATIC_NODES) ||
(flags & MPOL_F_RELATIVE_NODES))
return ERR_PTR(-EINVAL);
+ } else if (mode == MPOL_WEIGHTED_INTERLEAVE) {
+ /* weighted interleave requires a nodemask and weights > 0 */
+ if (nodes_empty(*nodes))
+ return ERR_PTR(-EINVAL);
+ if (args->il_weights) {
+ node = first_node(*nodes);
+ while (node != MAX_NUMNODES) {
+ if (!args->il_weights[node])
+ return ERR_PTR(-EINVAL);
+ node = next_node(node, *nodes);
+ }
+ } else if (!(args->mode_flags & MPOL_F_GWEIGHT))
+ return ERR_PTR(-EINVAL);
} else if (nodes_empty(*nodes))
return ERR_PTR(-EINVAL);

@@ -309,6 +323,17 @@ static struct mempolicy *mpol_new(struct mempolicy_args *args)
policy->home_node = args->home_node;
policy->wil.cur_weight = 0;

+ if (policy->mode == MPOL_WEIGHTED_INTERLEAVE && args->il_weights) {
+ policy->wil.cur_weight = 0;
+ /* Minimum weight value is always 1 */
+ memset(policy->wil.weights, 1, MAX_NUMNODES);
+ node = first_node(*nodes);
+ while (node != MAX_NUMNODES) {
+ policy->wil.weights[node] = args->il_weights[node];
+ node = next_node(node, *nodes);
+ }
+ }
+
return policy;
}

@@ -937,6 +962,17 @@ static void do_get_mempolicy_nodemask(struct mempolicy *pol, nodemask_t *nmask)
}
}

+static void do_get_mempolicy_il_weights(struct mempolicy *pol,
+ unsigned char weights[MAX_NUMNODES])
+{
+ if (pol->mode != MPOL_WEIGHTED_INTERLEAVE)
+ memset(weights, 0, MAX_NUMNODES);
+ else if (pol->flags & MPOL_F_GWEIGHT)
+ memcpy(weights, iw_table, MAX_NUMNODES);
+ else
+ memcpy(weights, pol->wil.weights, MAX_NUMNODES);
+}
+
/* Retrieve NUMA policy for a VMA assocated with a given address */
static long do_get_vma_mempolicy(unsigned long addr, int *addr_node,
struct mempolicy_args *args)
@@ -973,6 +1009,9 @@ static long do_get_vma_mempolicy(unsigned long addr, int *addr_node,
if (args->policy_nodes)
do_get_mempolicy_nodemask(pol, args->policy_nodes);

+ if (args->il_weights)
+ do_get_mempolicy_il_weights(pol, args->il_weights);
+
if (pol != &default_policy) {
mpol_put(pol);
mpol_cond_put(pol);
@@ -999,6 +1038,9 @@ static long do_get_task_mempolicy(struct mempolicy_args *args)
if (args->policy_nodes)
do_get_mempolicy_nodemask(pol, args->policy_nodes);

+ if (args->il_weights)
+ do_get_mempolicy_il_weights(pol, args->il_weights);
+
return 0;
}

@@ -1521,6 +1563,9 @@ static long kernel_mbind(unsigned long start, unsigned long len,
if (err)
return err;

+ if (mode & MPOL_WEIGHTED_INTERLEAVE)
+ mode_flags |= MPOL_F_GWEIGHT;
+
memset(&margs, 0, sizeof(margs));
margs.mode = lmode;
margs.mode_flags = mode_flags;
@@ -1611,6 +1656,8 @@ SYSCALL_DEFINE5(mbind2, unsigned long, start, unsigned long, len,
struct mempolicy_args margs;
nodemask_t policy_nodes;
unsigned long __user *nodes_ptr;
+ unsigned char weights[MAX_NUMNODES];
+ unsigned char __user *weights_ptr;
int err;

if (!start || !len)
@@ -1643,6 +1690,23 @@ SYSCALL_DEFINE5(mbind2, unsigned long, start, unsigned long, len,
return err;
margs.policy_nodes = &policy_nodes;

+ if (kargs.mode == MPOL_WEIGHTED_INTERLEAVE) {
+ weights_ptr = u64_to_user_ptr(kargs.il_weights);
+ if (weights_ptr) {
+ err = copy_struct_from_user(weights,
+ sizeof(weights),
+ weights_ptr,
+ kargs.pol_maxnodes);
+ if (err)
+ return err;
+ margs.il_weights = weights;
+ } else {
+ margs.il_weights = NULL;
+ margs.mode_flags |= MPOL_F_GWEIGHT;
+ }
+ } else
+ margs.il_weights = NULL;
+
return do_mbind(untagged_addr(start), len, &margs, flags);
}

@@ -1664,6 +1728,9 @@ static long kernel_set_mempolicy(int mode, const unsigned long __user *nmask,
if (err)
return err;

+ if (mode & MPOL_WEIGHTED_INTERLEAVE)
+ mode_flags |= MPOL_F_GWEIGHT;
+
memset(&args, 0, sizeof(args));
args.mode = lmode;
args.mode_flags = mode_flags;
@@ -1687,6 +1754,8 @@ SYSCALL_DEFINE3(set_mempolicy2, struct mpol_args __user *, uargs, size_t, usize,
int err;
nodemask_t policy_nodemask;
unsigned long __user *nodes_ptr;
+ unsigned char weights[MAX_NUMNODES];
+ unsigned char __user *weights_ptr;

if (flags)
return -EINVAL;
@@ -1712,6 +1781,20 @@ SYSCALL_DEFINE3(set_mempolicy2, struct mpol_args __user *, uargs, size_t, usize,
} else
margs.policy_nodes = NULL;

+ if (kargs.mode == MPOL_WEIGHTED_INTERLEAVE && kargs.il_weights) {
+ weights_ptr = u64_to_user_ptr(kargs.il_weights);
+ err = copy_struct_from_user(weights,
+ sizeof(weights),
+ weights_ptr,
+ kargs.pol_maxnodes);
+ if (err)
+ return err;
+ margs.il_weights = weights;
+ } else {
+ margs.il_weights = NULL;
+ margs.mode_flags |= MPOL_F_GWEIGHT;
+ }
+
return do_set_mempolicy(&margs);
}

@@ -1914,17 +1997,25 @@ SYSCALL_DEFINE4(get_mempolicy2, struct mpol_args __user *, uargs, size_t, usize,
int err;
nodemask_t policy_nodemask;
unsigned long __user *nodes_ptr;
+ unsigned char __user *weights_ptr;
+ unsigned char weights[MAX_NUMNODES];

if (flags & ~(MPOL_F_ADDR))
return -EINVAL;

/* initialize any memory liable to be copied to userland */
memset(&margs, 0, sizeof(margs));
+ memset(weights, 0, sizeof(weights));

err = copy_struct_from_user(&kargs, sizeof(kargs), uargs, usize);
if (err)
return -EINVAL;

+ if (kargs.il_weights)
+ margs.il_weights = weights;
+ else
+ margs.il_weights = NULL;
+
margs.policy_nodes = kargs.pol_nodes ? &policy_nodemask : NULL;
if (flags & MPOL_F_ADDR)
err = do_get_vma_mempolicy(untagged_addr(addr), NULL, &margs);
@@ -1946,6 +2037,13 @@ SYSCALL_DEFINE4(get_mempolicy2, struct mpol_args __user *, uargs, size_t, usize,
return err;
}

+ if (kargs.mode == MPOL_WEIGHTED_INTERLEAVE && kargs.il_weights) {
+ weights_ptr = u64_to_user_ptr(kargs.il_weights);
+ err = copy_to_user(weights_ptr, weights, kargs.pol_maxnodes);
+ if (err)
+ return err;
+ }
+
return copy_to_user(uargs, &kargs, usize) ? -EFAULT : 0;
}

@@ -2062,13 +2160,18 @@ static unsigned int weighted_interleave_nodes(struct mempolicy *policy)
{
unsigned int next;
struct task_struct *me = current;
+ unsigned char next_weight;

next = next_node_in(me->il_prev, policy->nodes);
if (next == MAX_NUMNODES)
return next;

- if (!policy->wil.cur_weight)
- policy->wil.cur_weight = iw_table[next];
+ if (!policy->wil.cur_weight) {
+ next_weight = (policy->flags & MPOL_F_GWEIGHT) ?
+ iw_table[next] :
+ policy->wil.weights[next];
+ policy->wil.cur_weight = next_weight ? next_weight : 1;
+ }

policy->wil.cur_weight--;
if (!policy->wil.cur_weight)
@@ -2142,6 +2245,7 @@ static unsigned int weighted_interleave_nid(struct mempolicy *pol, pgoff_t ilx)
nodemask_t nodemask = pol->nodes;
unsigned int target, weight_total = 0;
int nid;
+ unsigned char *pol_weights;
unsigned char weights[MAX_NUMNODES];
unsigned char weight;

@@ -2153,8 +2257,13 @@ static unsigned int weighted_interleave_nid(struct mempolicy *pol, pgoff_t ilx)
return nid;

/* Then collect weights on stack and calculate totals */
+ if (pol->flags & MPOL_F_GWEIGHT)
+ pol_weights = iw_table;
+ else
+ pol_weights = pol->wil.weights;
+
for_each_node_mask(nid, nodemask) {
- weight = iw_table[nid];
+ weight = pol_weights[nid];
weight_total += weight;
weights[nid] = weight;
}
@@ -2552,6 +2661,7 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp,
unsigned long nr_allocated;
unsigned long rounds;
unsigned long node_pages, delta;
+ unsigned char *pol_weights;
unsigned char weight;
unsigned char weights[MAX_NUMNODES];
unsigned int weight_total = 0;
@@ -2565,9 +2675,14 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp,

nnodes = nodes_weight(nodes);

+ if (pol->flags & MPOL_F_GWEIGHT)
+ pol_weights = iw_table;
+ else
+ pol_weights = pol->wil.weights;
+
/* Collect weights and save them on stack so they don't change */
for_each_node_mask(node, nodes) {
- weight = iw_table[node];
+ weight = pol_weights[node];
weight_total += weight;
weights[node] = weight;
}
@@ -3092,6 +3207,7 @@ void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
{
int ret;
struct mempolicy_args margs;
+ unsigned char weights[MAX_NUMNODES];

sp->root = RB_ROOT; /* empty tree == default mempolicy */
rwlock_init(&sp->lock);
@@ -3109,6 +3225,11 @@ void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol)
margs.mode_flags = mpol->flags;
margs.policy_nodes = &mpol->w.user_nodemask;
margs.home_node = NUMA_NO_NODE;
+ if (margs.mode == MPOL_WEIGHTED_INTERLEAVE &&
+ !(margs.mode_flags & MPOL_F_GWEIGHT)) {
+ memcpy(weights, mpol->wil.weights, sizeof(weights));
+ margs.il_weights = weights;
+ }

/* contextualize the tmpfs mount point mempolicy to this file */
npol = mpol_new(&margs);
--
2.39.1