Re: [PATCH 3/3] mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving

Huang, Ying
2024-01-18T03:07:58Z

Gregory Price <gourry.memverge@gmail.com> writes:

> When a system has multiple NUMA nodes and it becomes bandwidth hungry,
> using the current MPOL_INTERLEAVE could be an wise option.
>
> However, if those NUMA nodes consist of different types of memory such
> as socket-attached DRAM and CXL/PCIe attached DRAM, the round-robin
> based interleave policy does not optimally distribute data to make use
> of their different bandwidth characteristics.
>
> Instead, interleave is more effective when the allocation policy follows
> each NUMA nodes' bandwidth weight rather than a simple 1:1 distribution.
>
> This patch introduces a new memory policy, MPOL_WEIGHTED_INTERLEAVE,
> enabling weighted interleave between NUMA nodes. Weighted interleave
> allows for proportional distribution of memory across multiple numa
> nodes, preferably apportioned to match the bandwidth of each node.
>
> For example, if a system has 1 CPU node (0), and 2 memory nodes (0,1),
> with bandwidth of (100GB/s, 50GB/s) respectively, the appropriate
> weight distribution is (2:1).
>
> Weights for each node can be assigned via the new sysfs extension:
> /sys/kernel/mm/mempolicy/weighted_interleave/
>
> In addition, the `default_iw_table` is created, which will be extended
> in the future to allow defaults to be registered by drivers. For now,
> the default value of all nodes will be `1`, which matches the behavior
> of standard 1:1 round-robin interleave.
>
> The policy allocates a number of pages equal to the set weights. For
> example, if the weights are (2,1), then 2 pages will be allocated on
> node0 for every 1 page allocated on node1.
>
> The new flag MPOL_WEIGHTED_INTERLEAVE can be used in set_mempolicy(2)
> and mbind(2).
>
> There are 3 integration points:
>
> weighted_interleave_nodes:
> Counts the number of allocations as they occur, and applies the
> weight for the current node. When the weight reaches 0, switch
> to the next node.
>
> weighted_interleave_nid:
> Gets the total weight of the nodemask as well as each individual
> node weight, then calculates the node based on the given index.
>
> bulk_array_weighted_interleave:
> Gets the total weight of the nodemask as well as each individual
> node weight, then calculates the number of "interleave rounds" as
> well as any delta ("partial round"). Calculates the number of
> pages for each node and allocates them.
>
> If a node was scheduled for interleave via interleave_nodes, the
> current weight (pol->cur_weight) will be allocated first, before
> the remaining bulk calculation is done.
>
> One piece of complexity is the interaction between a recent refactor
> which split the logic to acquire the "ilx" (interleave index) of an
> allocation and the actually application of the interleave. The
> calculation of the `interleave index` is done by `get_vma_policy()`,
> while the actual selection of the node will be later appliex by the
> relevant weighted_interleave function.
>
> Suggested-by: Hasan Al Maruf <Hasan.Maruf@amd.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: Honggyu Kim <honggyu.kim@sk.com>
> Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
> Co-developed-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
> Signed-off-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
> Co-developed-by: Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
> Signed-off-by: Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
> Co-developed-by: Ravi Jonnalagadda <ravis.opensrc@micron.com>
> Signed-off-by: Ravi Jonnalagadda <ravis.opensrc@micron.com>
> ---
> .../admin-guide/mm/numa_memory_policy.rst | 9 +
> include/linux/mempolicy.h | 5 +
> include/uapi/linux/mempolicy.h | 1 +
> mm/mempolicy.c | 214 +++++++++++++++++-
> 4 files changed, 226 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/mm/numa_memory_policy.rst b/Documentation/admin-guide/mm/numa_memory_policy.rst
> index eca38fa81e0f..a70f20ce1ffb 100644
> --- a/Documentation/admin-guide/mm/numa_memory_policy.rst
> +++ b/Documentation/admin-guide/mm/numa_memory_policy.rst
> @@ -250,6 +250,15 @@ MPOL_PREFERRED_MANY
> can fall back to all existing numa nodes. This is effectively
> MPOL_PREFERRED allowed for a mask rather than a single node.
>
> +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/
> +
> + Weighted interleave allocates pages on nodes according to a
> + weight. For example if nodes [0,1] are weighted [5,2], 5 pages
> + will be allocated on node0 for every 2 pages allocated on node1.
> +
> NUMA memory policy supports the following optional mode flags:
>
> MPOL_F_STATIC_NODES
> diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
> index 931b118336f4..c1a083eb0dd5 100644
> --- a/include/linux/mempolicy.h
> +++ b/include/linux/mempolicy.h
> @@ -54,6 +54,11 @@ struct mempolicy {
> nodemask_t cpuset_mems_allowed; /* relative to these nodes */
> nodemask_t user_nodemask; /* nodemask passed by user */
> } w;
> +
> + /* Weighted interleave settings */
> + struct {
> + u8 cur_weight;
> + } wil;
> };
>
> /*
> diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h
> index a8963f7ef4c2..1f9bb10d1a47 100644
> --- a/include/uapi/linux/mempolicy.h
> +++ b/include/uapi/linux/mempolicy.h
> @@ -23,6 +23,7 @@ enum {
> MPOL_INTERLEAVE,
> MPOL_LOCAL,
> MPOL_PREFERRED_MANY,
> + MPOL_WEIGHTED_INTERLEAVE,
> MPOL_MAX, /* always last member of enum */
> };
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 0abd3a3394ef..a2b5d64b28e0 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -19,6 +19,13 @@
> * for anonymous memory. For process policy an process counter
> * is used.
> *
> + * weighted interleave
> + * Allocate memory interleaved over a set of nodes based on
> + * a set of weights (per-node), with normal fallback if it
> + * fails. Otherwise operates the same as interleave.
> + * Example: nodeset(0,1) & weights (2,1) - 2 pages allocated
> + * on node 0 for every 1 page allocated on node 1.
> + *
> * bind Only allocate memory on a specific set of nodes,
> * no fallback.
> * FIXME: memory is allocated starting with the first node
> @@ -327,6 +334,7 @@ static struct mempolicy *mpol_new(unsigned short mode, unsigned short flags,
> policy->mode = mode;
> policy->flags = flags;
> policy->home_node = NUMA_NO_NODE;
> + policy->wil.cur_weight = 0;
>
> return policy;
> }
> @@ -439,6 +447,10 @@ static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
> .create = mpol_new_nodemask,
> .rebind = mpol_rebind_preferred,
> },
> + [MPOL_WEIGHTED_INTERLEAVE] = {
> + .create = mpol_new_nodemask,
> + .rebind = mpol_rebind_nodemask,
> + },
> };
>
> static bool migrate_folio_add(struct folio *folio, struct list_head *foliolist,
> @@ -860,7 +872,8 @@ static long do_set_mempolicy(unsigned short mode, unsigned short flags,
>
> old = current->mempolicy;
> current->mempolicy = new;
> - if (new && new->mode == MPOL_INTERLEAVE)
> + if (new && (new->mode == MPOL_INTERLEAVE ||
> + new->mode == MPOL_WEIGHTED_INTERLEAVE))
> current->il_prev = MAX_NUMNODES-1;
> task_unlock(current);
> mpol_put(old);
> @@ -886,6 +899,7 @@ static void get_policy_nodemask(struct mempolicy *pol, nodemask_t *nodes)
> case MPOL_INTERLEAVE:
> case MPOL_PREFERRED:
> case MPOL_PREFERRED_MANY:
> + case MPOL_WEIGHTED_INTERLEAVE:
> *nodes = pol->nodes;
> break;
> case MPOL_LOCAL:
> @@ -970,6 +984,13 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
> } else if (pol == current->mempolicy &&
> pol->mode == MPOL_INTERLEAVE) {
> *policy = next_node_in(current->il_prev, pol->nodes);
> + } else if (pol == current->mempolicy &&
> + (pol->mode == MPOL_WEIGHTED_INTERLEAVE)) {
> + if (pol->wil.cur_weight)
> + *policy = current->il_prev;
> + else
> + *policy = next_node_in(current->il_prev,
> + pol->nodes);
> } else {
> err = -EINVAL;
> goto out;
> @@ -1799,7 +1820,8 @@ struct mempolicy *get_vma_policy(struct vm_area_struct *vma,
> pol = __get_vma_policy(vma, addr, ilx);
> if (!pol)
> pol = get_task_policy(current);
> - if (pol->mode == MPOL_INTERLEAVE) {
> + if (pol->mode == MPOL_INTERLEAVE ||
> + pol->mode == MPOL_WEIGHTED_INTERLEAVE) {
> *ilx += vma->vm_pgoff >> order;
> *ilx += (addr - vma->vm_start) >> (PAGE_SHIFT + order);
> }
> @@ -1849,6 +1871,28 @@ bool apply_policy_zone(struct mempolicy *policy, enum zone_type zone)
> return zone >= dynamic_policy_zone;
> }
>
> +static unsigned int weighted_interleave_nodes(struct mempolicy *policy)
> +{
> + unsigned int next;
> + struct task_struct *me = current;
> + struct iw_table __rcu *table;
> +
> + next = next_node_in(me->il_prev, policy->nodes);
> + if (next == MAX_NUMNODES)
> + return next;
> +
> + rcu_read_lock();
> + table = rcu_dereference(iw_table);
> + if (!policy->wil.cur_weight)
> + policy->wil.cur_weight = table->weights[next];
> + rcu_read_unlock();
> +
> + policy->wil.cur_weight--;
> + if (!policy->wil.cur_weight)
> + me->il_prev = next;
> + return next;
> +}
> +
> /* Do dynamic interleaving for a process */
> static unsigned int interleave_nodes(struct mempolicy *policy)
> {
> @@ -1883,6 +1927,9 @@ unsigned int mempolicy_slab_node(void)
> case MPOL_INTERLEAVE:
> return interleave_nodes(policy);
>
> + case MPOL_WEIGHTED_INTERLEAVE:
> + return weighted_interleave_nodes(policy);
> +
> case MPOL_BIND:
> case MPOL_PREFERRED_MANY:
> {
> @@ -1921,6 +1968,39 @@ static unsigned int read_once_policy_nodemask(struct mempolicy *pol,
> return nodes_weight(*mask);
> }
>
> +static unsigned int weighted_interleave_nid(struct mempolicy *pol, pgoff_t ilx)
> +{
> + nodemask_t nodemask;
> + unsigned int target, nr_nodes;
> + struct iw_table __rcu *table;
> + unsigned int weight_total = 0;
> + u8 weight;
> + int nid;
> +
> + nr_nodes = read_once_policy_nodemask(pol, &nodemask);
> + if (!nr_nodes)
> + return numa_node_id();
> +
> + rcu_read_lock();
> + table = rcu_dereference(iw_table);
> + /* calculate the total weight */
> + for_each_node_mask(nid, nodemask)
> + weight_total += table->weights[nid];
> +
> + /* Calculate the node offset based on totals */
> + target = ilx % weight_total;
> + nid = first_node(nodemask);
> + while (target) {
> + weight = table->weights[nid];
> + if (target < weight)
> + break;
> + target -= weight;
> + nid = next_node_in(nid, nodemask);
> + }
> + rcu_read_unlock();
> + return nid;
> +}
> +
> /*
> * Do static interleaving for interleave index @ilx. Returns the ilx'th
> * node in pol->nodes (starting from ilx=0), wrapping around if ilx
> @@ -1981,6 +2061,11 @@ static nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *pol,
> *nid = (ilx == NO_INTERLEAVE_INDEX) ?
> interleave_nodes(pol) : interleave_nid(pol, ilx);
> break;
> + case MPOL_WEIGHTED_INTERLEAVE:
> + *nid = (ilx == NO_INTERLEAVE_INDEX) ?
> + weighted_interleave_nodes(pol) :
> + weighted_interleave_nid(pol, ilx);
> + break;
> }
>
> return nodemask;
> @@ -2042,6 +2127,7 @@ bool init_nodemask_of_mempolicy(nodemask_t *mask)
> case MPOL_PREFERRED_MANY:
> case MPOL_BIND:
> case MPOL_INTERLEAVE:
> + case MPOL_WEIGHTED_INTERLEAVE:
> *mask = mempolicy->nodes;
> break;
>
> @@ -2141,7 +2227,8 @@ struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order,
> * If the policy is interleave or does not allow the current
> * node in its nodemask, we allocate the standard way.
> */
> - if (pol->mode != MPOL_INTERLEAVE &&
> + if ((pol->mode != MPOL_INTERLEAVE &&
> + pol->mode != MPOL_WEIGHTED_INTERLEAVE) &&
> (!nodemask || node_isset(nid, *nodemask))) {
> /*
> * First, try to allocate THP only on local node, but
> @@ -2277,6 +2364,114 @@ static unsigned long alloc_pages_bulk_array_interleave(gfp_t gfp,
> return total_allocated;
> }
>
> +static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp,
> + struct mempolicy *pol, unsigned long nr_pages,
> + struct page **page_array)
> +{
> + struct task_struct *me = current;
> + unsigned long total_allocated = 0;
> + unsigned long nr_allocated;
> + unsigned long rounds;
> + unsigned long node_pages, delta;
> + u8 weight;
> + struct iw_table __rcu *table;
> + u8 *weights;
> + unsigned int weight_total = 0;
> + unsigned long rem_pages = nr_pages;
> + nodemask_t nodes;
> + int nnodes, node, weight_nodes;
> + int prev_node = NUMA_NO_NODE;
> + int i;
> +
> + nnodes = read_once_policy_nodemask(pol, &nodes);
> + if (!nnodes)
> + return 0;
> +
> + /* Continue allocating from most recent node and adjust the nr_pages */
> + if (pol->wil.cur_weight) {
> + node = next_node_in(me->il_prev, nodes);
> + node_pages = pol->wil.cur_weight;
> + if (node_pages > rem_pages)
> + node_pages = rem_pages;
> + nr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,
> + NULL, page_array);
> + page_array += nr_allocated;
> + total_allocated += nr_allocated;
> + /* if that's all the pages, no need to interleave */
> + if (rem_pages <= pol->wil.cur_weight) {
> + pol->wil.cur_weight -= rem_pages;
> + return total_allocated;
> + }
> + /* Otherwise we adjust nr_pages down, and continue from there */
> + rem_pages -= pol->wil.cur_weight;
> + pol->wil.cur_weight = 0;
> + prev_node = node;
> + }
> +
> + /* fetch the weights for this operation and calculate total weight */
> + weights = kmalloc(nnodes, GFP_KERNEL);
> + if (!weights)
> + return total_allocated;
> +
> + rcu_read_lock();
> + table = rcu_dereference(iw_table);
> + weight_nodes = 0;
> + for_each_node_mask(node, nodes) {
> + weights[weight_nodes++] = table->weights[node];
> + weight_total += table->weights[node];
> + }
> + rcu_read_unlock();
> +
> + if (!weight_total) {
> + kfree(weights);
> + return total_allocated;
> + }
> +
> + /* Now we can continue allocating as if from 0 instead of an offset */
> + rounds = rem_pages / weight_total;
> + delta = rem_pages % weight_total;
> + for (i = 0; i < nnodes; i++) {
> + node = next_node_in(prev_node, nodes);
> + weight = weights[i];
> + node_pages = weight * rounds;
> + if (delta) {
> + if (delta > weight) {
> + node_pages += weight;
> + delta -= weight;
> + } else {
> + node_pages += delta;
> + delta = 0;
> + }
> + }
> + nr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,
> + NULL, page_array);
> + page_array += nr_allocated;
> + total_allocated += nr_allocated;
> + if (total_allocated == nr_pages)
> + break;
> + prev_node = node;
> + }
> +
> + /*
> + * Finally, we need to update me->il_prev and pol->wil.cur_weight
> + * if there were overflow pages, but not equivalent to the node
> + * weight, set the cur_weight to node_weight - delta and the
> + * me->il_prev to the previous node. Otherwise if it was perfect
> + * we can simply set il_prev to node and cur_weight to 0
> + */
> + if (node_pages) {
> + me->il_prev = prev_node;
> + node_pages %= weight;
> + pol->wil.cur_weight = weight - node_pages;
> + } else {
> + me->il_prev = node;
> + pol->wil.cur_weight = 0;
> + }

It appears that we should set me->il_prev and pol->wil.cur_weight when
delta becomes 0? That is, following allocation should start from there?

--
Best Regards,
Huang, Ying

> +
> + kfree(weights);
> + return total_allocated;
> +}
> +
> static unsigned long alloc_pages_bulk_array_preferred_many(gfp_t gfp, int nid,
> struct mempolicy *pol, unsigned long nr_pages,
> struct page **page_array)
> @@ -2317,6 +2512,11 @@ unsigned long alloc_pages_bulk_array_mempolicy(gfp_t gfp,
> return alloc_pages_bulk_array_interleave(gfp, pol,
> nr_pages, page_array);
>
> + if (pol->mode == MPOL_WEIGHTED_INTERLEAVE)
> + return alloc_pages_bulk_array_weighted_interleave(gfp, pol,
> + nr_pages,
> + page_array);
> +
> if (pol->mode == MPOL_PREFERRED_MANY)
> return alloc_pages_bulk_array_preferred_many(gfp,
> numa_node_id(), pol, nr_pages, page_array);
> @@ -2392,6 +2592,7 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
> case MPOL_INTERLEAVE:
> case MPOL_PREFERRED:
> case MPOL_PREFERRED_MANY:
> + case MPOL_WEIGHTED_INTERLEAVE:
> return !!nodes_equal(a->nodes, b->nodes);
> case MPOL_LOCAL:
> return true;
> @@ -2528,6 +2729,10 @@ int mpol_misplaced(struct folio *folio, struct vm_area_struct *vma,
> polnid = interleave_nid(pol, ilx);
> break;
>
> + case MPOL_WEIGHTED_INTERLEAVE:
> + polnid = weighted_interleave_nid(pol, ilx);
> + break;
> +
> case MPOL_PREFERRED:
> if (node_isset(curnid, pol->nodes))
> goto out;
> @@ -2902,6 +3107,7 @@ static const char * const policy_modes[] =
> [MPOL_PREFERRED] = "prefer",
> [MPOL_BIND] = "bind",
> [MPOL_INTERLEAVE] = "interleave",
> + [MPOL_WEIGHTED_INTERLEAVE] = "weighted interleave",
> [MPOL_LOCAL] = "local",
> [MPOL_PREFERRED_MANY] = "prefer (many)",
> };
> @@ -2961,6 +3167,7 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
> }
> break;
> case MPOL_INTERLEAVE:
> + case MPOL_WEIGHTED_INTERLEAVE:
> /*
> * Default to online nodes with memory if no nodelist
> */
> @@ -3071,6 +3278,7 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
> case MPOL_PREFERRED_MANY:
> case MPOL_BIND:
> case MPOL_INTERLEAVE:
> + case MPOL_WEIGHTED_INTERLEAVE:
> nodes = pol->nodes;
> break;