Gregory Price <gourry.memverge@xxxxxxxxx> writes:
> When a system has multiple NUMA nodes and it becomes bandwidth hungry,
> the current MPOL_INTERLEAVE could be an wise option.
>
> However, if those NUMA nodes consist of different types of memory such
> as having local DRAM and CXL memory together, the current round-robin
> based interleaving policy doesn't maximize the overall bandwidth because
> of their different bandwidth characteristics.
>
> Instead, the interleaving can be more efficient when the allocation
> policy follows each NUMA nodes' bandwidth weight rather than having 1:1
> round-robin allocation.
>
> This patch introduces a new memory policy, MPOL_WEIGHTED_INTERLEAVE, which
> enables weighted interleaving between NUMA nodes. Weighted interleave
> allows for a proportional distribution of memory across multiple numa
> nodes, preferablly apportioned to match the bandwidth capacity of each
> node from the perspective of the accessing node.
>
> For example, if a system has 1 CPU node (0), and 2 memory nodes (0,1),
> with a relative bandwidth of (100GB/s, 50GB/s) respectively, the
> appropriate weight distribution is (2:1).
>
> Weights will be acquired from the global weight matrix exposed by the
> sysfs extension: /sys/kernel/mm/mempolicy/weighted_interleave/
>
> The policy will then allocate the number of pages according 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. Applied by `mempolicy_slab_node()` and
> `policy_nodemask()`
>
> 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.
> Applied by `policy_nodemask()` and `mpol_misplaced()`
>
> 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. This simplifies the
> calculation at the cost of an additional allocation call.
>
> 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.
>
> If CONFIG_SYSFS is disabled, the weight table will be initialized
> to set all nodes to weight 1, but the weighting code is still called.
> This is so that task-local weights (future patch) can still be
> engaged cleanly without ifdef spaghetti.
>
> Suggested-by: Hasan Al Maruf <Hasan.Maruf@xxxxxxx>
> Signed-off-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
> Co-developed-by: Rakie Kim <rakie.kim@xxxxxx>
> Signed-off-by: Rakie Kim <rakie.kim@xxxxxx>
> Co-developed-by: Honggyu Kim <honggyu.kim@xxxxxx>
> Signed-off-by: Honggyu Kim <honggyu.kim@xxxxxx>
> Co-developed-by: Hyeongtak Ji <hyeongtak.ji@xxxxxx>
> Signed-off-by: Hyeongtak Ji <hyeongtak.ji@xxxxxx>
> Co-developed-by: Srinivasulu Thanneeru <sthanneeru.opensrc@xxxxxxxxxx>
> Signed-off-by: Srinivasulu Thanneeru <sthanneeru.opensrc@xxxxxxxxxx>
> Co-developed-by: Ravi Jonnalagadda <ravis.opensrc@xxxxxxxxxx>
> Signed-off-by: Ravi Jonnalagadda <ravis.opensrc@xxxxxxxxxx>
> ---
> .../admin-guide/mm/numa_memory_policy.rst | 11 +
> include/linux/mempolicy.h | 5 +
> include/uapi/linux/mempolicy.h | 1 +
> mm/mempolicy.c | 197 +++++++++++++++++-
> 4 files changed, 211 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..d2c8e712785b 100644
> --- a/Documentation/admin-guide/mm/numa_memory_policy.rst
> +++ b/Documentation/admin-guide/mm/numa_memory_policy.rst
> @@ -250,6 +250,17 @@ 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 allocations pages on nodes according to
> + their weight. For example if nodes [0,1] are weighted [5,2]
> + respectively, 5 pages will be allocated on node0 for every
> + 2 pages allocated on node1. This can better distribute data
> + according to bandwidth on heterogeneous memory systems.
> +
> 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..ba09167e80f7 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 {
> + unsigned char 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 0e77633b07a5..0a180c670f0c 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -305,6 +305,7 @@ 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;
> }
> @@ -417,6 +418,10 @@ 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,
> @@ -838,7 +843,8 @@ 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);
> @@ -864,6 +870,7 @@ 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:
> @@ -948,6 +955,13 @@ 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;
> @@ -1777,7 +1791,8 @@ 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);
> }
> @@ -1827,6 +1842,24 @@ 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;
> +
> + 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];
> +
> + 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)
> {
> @@ -1861,6 +1894,9 @@ 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:
> {
> @@ -1885,6 +1921,41 @@ unsigned int mempolicy_slab_node(void)
> }
> }
>
> +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 weights[MAX_NUMNODES];
MAX_NUMNODSE could be as large as 1024. 1KB stack space may be too
large?
> + unsigned char weight;
> +
> + barrier();
Memory barrier needs comments.
> +
> + /* first ensure we have a valid nodemask */
> + nid = first_node(nodemask);
> + if (nid == MAX_NUMNODES)
> + return nid;
It appears that this isn't necessary, because we can check whether
weight_total == 0 after the next loop.
> +
> + /* Then collect weights on stack and calculate totals */
> + for_each_node_mask(nid, nodemask) {
> + weight = iw_table[nid];
> + weight_total += weight;
> + weights[nid] = weight;
> + }
> +
> + /* Finally, calculate the node offset based on totals */
> + target = (unsigned int)ilx % weight_total;
Why use type casting?
> + nid = first_node(nodemask);
> + while (target) {
> + weight = weights[nid];
> + if (target < weight)
> + break;
> + target -= weight;
> + nid = next_node_in(nid, nodemask);
> + }
> + 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
> @@ -1953,6 +2024,11 @@ 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;
> @@ -2014,6 +2090,7 @@ 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;
>
> @@ -2113,7 +2190,8 @@ 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
> @@ -2249,6 +2327,106 @@ 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;
> + unsigned char weight;
> + unsigned char weights[MAX_NUMNODES];
> + unsigned int weight_total = 0;
> + unsigned long rem_pages = nr_pages;
> + nodemask_t nodes = pol->nodes;
> + int nnodes, node, prev_node;
> + int i;
> +
> + /* Stabilize the nodemask on the stack */
> + barrier();
I don't think barrier() is needed to wait for memory operations for
stack. It's usually used for cross-processor memory order.
> +
> + nnodes = nodes_weight(nodes);
> +
> + /* Collect weights and save them on stack so they don't change */
> + for_each_node_mask(node, nodes) {
> + weight = iw_table[node];
> + weight_total += weight;
> + weights[node] = weight;
> + }
> +
> + /* 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;
If pol->wil.cur_weight == 0, prev_node will be used without being
initialized below.
> + }
> +
> + /* 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[node];
> + node_pages = weight * rounds;
> + if (delta) {
> + if (delta > weight) {
> + node_pages += weight;
> + delta -= weight;
> + } else {
> + node_pages += delta;
> + delta = 0;
> + }
> + }
> + /* We may not make it all the way around */
> + if (!node_pages)
> + break;
> + /* If an over-allocation would occur, floor it */
> + if (node_pages + total_allocated > nr_pages) {
Why is this possible?
> + node_pages = nr_pages - total_allocated;
> + delta = 0;
> + }
> + nr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,
> + NULL, page_array);
> + page_array += nr_allocated;
> + total_allocated += nr_allocated;
> + 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;
> + }
> +
> + 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)
> @@ -2289,6 +2467,11 @@ 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);
> @@ -2364,6 +2547,7 @@ 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;
> @@ -2500,6 +2684,10 @@ 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;
> @@ -2874,6 +3062,7 @@ 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)",
> };
> @@ -2933,6 +3122,7 @@ 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
> */
> @@ -3043,6 +3233,7 @@ 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;
> default:
--
Best Regards,
Huang, Ying
