Re: [PATCHv5 04/10] node: Link memory nodes to their compute nodes

Rafael J. Wysocki
2019-02-07T11:35:43Z

On Fri, Jan 25, 2019 at 12:08 AM Keith Busch <keith.busch@intel.com> wrote:
>
> Systems may be constructed with various specialized nodes. Some nodes
> may provide memory, some provide compute devices that access and use
> that memory, and others may provide both. Nodes that provide memory are
> referred to as memory targets, and nodes that can initiate memory access
> are referred to as memory initiators.
>
> Memory targets will often have varying access characteristics from
> different initiators, and platforms may have ways to express those
> relationships. In preparation for these systems, provide interfaces for
> the kernel to export the memory relationship among different nodes memory
> targets and their initiators with symlinks to each other.
>
> If a system provides access locality for each initiator-target pair, nodes
> may be grouped into ranked access classes relative to other nodes. The
> new interface allows a subsystem to register relationships of varying
> classes if available and desired to be exported.
>
> A memory initiator may have multiple memory targets in the same access
> class. The target memory's initiators in a given class indicate the
> nodes access characteristics share the same performance relative to other
> linked initiator nodes. Each target within an initiator's access class,
> though, do not necessarily perform the same as each other.
>
> A memory target node may have multiple memory initiators. All linked
> initiators in a target's class have the same access characteristics to
> that target.
>
> The following example show the nodes' new sysfs hierarchy for a memory
> target node 'Y' with access class 0 from initiator node 'X':
>
> # symlinks -v /sys/devices/system/node/nodeX/access0/
> relative: /sys/devices/system/node/nodeX/access0/targets/nodeY -> ../../nodeY
>
> # symlinks -v /sys/devices/system/node/nodeY/access0/
> relative: /sys/devices/system/node/nodeY/access0/initiators/nodeX -> ../../nodeX
>
> The new attributes are added to the sysfs stable documentation.
>
> Signed-off-by: Keith Busch <keith.busch@intel.com>

Overall, if you decide to go for full struct device embedded in struct
node_access_nodes, feel free to add

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

to this patch.

> ---
> Documentation/ABI/stable/sysfs-devices-node | 25 ++++-
> drivers/base/node.c | 142 +++++++++++++++++++++++++++-
> include/linux/node.h | 7 +-
> 3 files changed, 171 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node
> index 3e90e1f3bf0a..fb843222a281 100644
> --- a/Documentation/ABI/stable/sysfs-devices-node
> +++ b/Documentation/ABI/stable/sysfs-devices-node
> @@ -90,4 +90,27 @@ Date: December 2009
> Contact: Lee Schermerhorn <lee.schermerhorn@hp.com>
> Description:
> The node's huge page size control/query attributes.
> - See Documentation/admin-guide/mm/hugetlbpage.rst
> \ No newline at end of file
> + See Documentation/admin-guide/mm/hugetlbpage.rst
> +
> +What: /sys/devices/system/node/nodeX/accessY/
> +Date: December 2018
> +Contact: Keith Busch <keith.busch@intel.com>
> +Description:
> + The node's relationship to other nodes for access class "Y".
> +
> +What: /sys/devices/system/node/nodeX/accessY/initiators/
> +Date: December 2018
> +Contact: Keith Busch <keith.busch@intel.com>
> +Description:
> + The directory containing symlinks to memory initiator
> + nodes that have class "Y" access to this target node's
> + memory. CPUs and other memory initiators in nodes not in
> + the list accessing this node's memory may have different
> + performance.
> +
> +What: /sys/devices/system/node/nodeX/classY/targets/
> +Date: December 2018
> +Contact: Keith Busch <keith.busch@intel.com>
> +Description:
> + The directory containing symlinks to memory targets that
> + this initiator node has class "Y" access.
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 86d6cd92ce3d..6f4097680580 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -17,6 +17,7 @@
> #include <linux/nodemask.h>
> #include <linux/cpu.h>
> #include <linux/device.h>
> +#include <linux/pm_runtime.h>
> #include <linux/swap.h>
> #include <linux/slab.h>
>
> @@ -59,6 +60,94 @@ static inline ssize_t node_read_cpulist(struct device *dev,
> static DEVICE_ATTR(cpumap, S_IRUGO, node_read_cpumask, NULL);
> static DEVICE_ATTR(cpulist, S_IRUGO, node_read_cpulist, NULL);
>
> +/**
> + * struct node_access_nodes - Access class device to hold user visible
> + * relationships to other nodes.
> + * @dev: Device for this memory access class
> + * @list_node: List element in the node's access list
> + * @access: The access class rank
> + */
> +struct node_access_nodes {
> + struct device dev;
> + struct list_head list_node;
> + unsigned access;
> +};
> +#define to_access_nodes(dev) container_of(dev, struct node_access_nodes, dev)
> +
> +static struct attribute *node_init_access_node_attrs[] = {
> + NULL,
> +};
> +
> +static struct attribute *node_targ_access_node_attrs[] = {
> + NULL,
> +};
> +
> +static const struct attribute_group initiators = {
> + .name = "initiators",
> + .attrs = node_init_access_node_attrs,
> +};
> +
> +static const struct attribute_group targets = {
> + .name = "targets",
> + .attrs = node_targ_access_node_attrs,
> +};
> +
> +static const struct attribute_group *node_access_node_groups[] = {
> + &initiators,
> + &targets,
> + NULL,
> +};
> +
> +static void node_remove_accesses(struct node *node)
> +{
> + struct node_access_nodes *c, *cnext;
> +
> + list_for_each_entry_safe(c, cnext, &node->access_list, list_node) {
> + list_del(&c->list_node);
> + device_unregister(&c->dev);
> + }
> +}
> +
> +static void node_access_release(struct device *dev)
> +{
> + kfree(to_access_nodes(dev));
> +}
> +
> +static struct node_access_nodes *node_init_node_access(struct node *node,
> + unsigned access)
> +{
> + struct node_access_nodes *access_node;
> + struct device *dev;
> +
> + list_for_each_entry(access_node, &node->access_list, list_node)
> + if (access_node->access == access)
> + return access_node;
> +
> + access_node = kzalloc(sizeof(*access_node), GFP_KERNEL);
> + if (!access_node)
> + return NULL;
> +
> + access_node->access = access;
> + dev = &access_node->dev;
> + dev->parent = &node->dev;
> + dev->release = node_access_release;
> + dev->groups = node_access_node_groups;
> + if (dev_set_name(dev, "access%u", access))
> + goto free;
> +
> + if (device_register(dev))
> + goto free_name;
> +
> + pm_runtime_no_callbacks(dev);
> + list_add_tail(&access_node->list_node, &node->access_list);
> + return access_node;
> +free_name:
> + kfree_const(dev->kobj.name);
> +free:
> + kfree(access_node);
> + return NULL;
> +}
> +
> #define K(x) ((x) << (PAGE_SHIFT - 10))
> static ssize_t node_read_meminfo(struct device *dev,
> struct device_attribute *attr, char *buf)
> @@ -340,7 +429,7 @@ static int register_node(struct node *node, int num)
> void unregister_node(struct node *node)
> {
> hugetlb_unregister_node(node); /* no-op, if memoryless node */
> -
> + node_remove_accesses(node);
> device_unregister(&node->dev);
> }
>
> @@ -372,6 +461,56 @@ int register_cpu_under_node(unsigned int cpu, unsigned int nid)
> kobject_name(&node_devices[nid]->dev.kobj));
> }
>
> +/**
> + * register_memory_node_under_compute_node - link memory node to its compute
> + * node for a given access class.
> + * @mem_node: Memory node number
> + * @cpu_node: Cpu node number
> + * @access: Access class to register
> + *
> + * Description:
> + * For use with platforms that may have separate memory and compute nodes.
> + * This function will export node relationships linking which memory
> + * initiator nodes can access memory targets at a given ranked access
> + * class.
> + */
> +int register_memory_node_under_compute_node(unsigned int mem_nid,
> + unsigned int cpu_nid,
> + unsigned access)
> +{
> + struct node *init_node, *targ_node;
> + struct node_access_nodes *initiator, *target;
> + int ret;
> +
> + if (!node_online(cpu_nid) || !node_online(mem_nid))
> + return -ENODEV;
> +
> + init_node = node_devices[cpu_nid];
> + targ_node = node_devices[mem_nid];
> + initiator = node_init_node_access(init_node, access);
> + target = node_init_node_access(targ_node, access);
> + if (!initiator || !target)
> + return -ENOMEM;
> +
> + ret = sysfs_add_link_to_group(&initiator->dev.kobj, "targets",
> + &targ_node->dev.kobj,
> + dev_name(&targ_node->dev));
> + if (ret)
> + return ret;
> +
> + ret = sysfs_add_link_to_group(&target->dev.kobj, "initiators",
> + &init_node->dev.kobj,
> + dev_name(&init_node->dev));
> + if (ret)
> + goto err;
> +
> + return 0;
> + err:
> + sysfs_remove_link_from_group(&initiator->dev.kobj, "targets",
> + dev_name(&targ_node->dev));
> + return ret;
> +}
> +
> int unregister_cpu_under_node(unsigned int cpu, unsigned int nid)
> {
> struct device *obj;
> @@ -580,6 +719,7 @@ int __register_one_node(int nid)
> register_cpu_under_node(cpu, nid);
> }
>
> + INIT_LIST_HEAD(&node_devices[nid]->access_list);
> /* initialize work queue for memory hot plug */
> init_node_hugetlb_work(nid);
>
> diff --git a/include/linux/node.h b/include/linux/node.h
> index 257bb3d6d014..f34688a203c1 100644
> --- a/include/linux/node.h
> +++ b/include/linux/node.h
> @@ -17,11 +17,12 @@
>
> #include <linux/device.h>
> #include <linux/cpumask.h>
> +#include <linux/list.h>
> #include <linux/workqueue.h>
>
> struct node {
> struct device dev;
> -
> + struct list_head access_list;
> #if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_HUGETLBFS)
> struct work_struct node_work;
> #endif
> @@ -75,6 +76,10 @@ extern int register_mem_sect_under_node(struct memory_block *mem_blk,
> extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk,
> unsigned long phys_index);
>
> +extern int register_memory_node_under_compute_node(unsigned int mem_nid,
> + unsigned int cpu_nid,
> + unsigned access);
> +
> #ifdef CONFIG_HUGETLBFS
> extern void register_hugetlbfs_with_node(node_registration_func_t doregister,
> node_registration_func_t unregister);
> --
> 2.14.4
>