node: Add heterogenous memory access attributes

Heterogeneous memory systems provide memory nodes with different latency
and bandwidth performance attributes. Provide a new kernel interface
for subsystems to register the attributes under the memory target
node's initiator access class. If the system provides this information,
applications may query these attributes when deciding which node to
request memory.

The following example shows the new sysfs hierarchy for a node exporting
performance attributes:

  # tree -P "read*|write*"/sys/devices/system/node/nodeY/accessZ/initiators/
  /sys/devices/system/node/nodeY/accessZ/initiators/
  |-- read_bandwidth
  |-- read_latency
  |-- write_bandwidth
  `-- write_latency

The bandwidth is exported as MB/s and latency is reported in
nanoseconds. The values are taken from the platform as reported by the
manufacturer.

Memory accesses from an initiator node that is not one of the memory's
access "Z" initiator nodes linked in the same directory may observe
different performance than reported here. When a subsystem makes use
of this interface, initiators of a different access number may not have
the same performance relative to initiators in other access numbers, or
omitted from the any access class' initiators.

Descriptions for memory access initiator performance access attributes
are added to sysfs stable documentation.

Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Brice Goglin <Brice.Goglin@inria.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node
index 433bcc04e542fb88d4d42f9f84d362081f9108d6..735a40a3f9b23b53e217b2c8de881239a9aa1ae1 100644 (file)
--- a/Documentation/ABI/stable/sysfs-devices-node
+++ b/Documentation/ABI/stable/sysfs-devices-node
@@ -114,3 +114,31 @@ Contact:   Keith Busch <keith.busch@intel.com>
 Description:
                The directory containing symlinks to memory targets that
                this initiator node has class "Y" access.
+
+What:          /sys/devices/system/node/nodeX/accessY/initiators/read_bandwidth
+Date:          December 2018
+Contact:       Keith Busch <keith.busch@intel.com>
+Description:
+               This node's read bandwidth in MB/s when accessed from
+               nodes found in this access class's linked initiators.
+
+What:          /sys/devices/system/node/nodeX/accessY/initiators/read_latency
+Date:          December 2018
+Contact:       Keith Busch <keith.busch@intel.com>
+Description:
+               This node's read latency in nanoseconds when accessed
+               from nodes found in this access class's linked initiators.
+
+What:          /sys/devices/system/node/nodeX/accessY/initiators/write_bandwidth
+Date:          December 2018
+Contact:       Keith Busch <keith.busch@intel.com>
+Description:
+               This node's write bandwidth in MB/s when accessed from
+               found in this access class's linked initiators.
+
+What:          /sys/devices/system/node/nodeX/accessY/initiators/write_latency
+Date:          December 2018
+Contact:       Keith Busch <keith.busch@intel.com>
+Description:
+               This node's write latency in nanoseconds when access
+               from nodes found in this class's linked initiators.

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 9fb2c4c92340b7e674e2fece4c90581d3059e502..1d47ab98741381e6efb8d999e6c8149b15a00196 100644 (file)
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -148,6 +148,14 @@ config DEBUG_TEST_DRIVER_REMOVE
          unusable. You should say N here unless you are explicitly looking to
          test this functionality.
 
+config HMEM_REPORTING
+       bool
+       default n
+       depends on NUMA
+       help
+         Enable reporting for heterogenous memory access attributes under
+         their non-uniform memory nodes.
+
 source "drivers/base/test/Kconfig"
 
 config SYS_HYPERVISOR

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 6f40976805805d40b3ad233c98f64b1f40ba2045..2de546a040a5c949fce04fc3548d72ac1bd7158a 100644 (file)
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -71,6 +71,9 @@ struct node_access_nodes {
        struct device           dev;
        struct list_head        list_node;
        unsigned                access;
+#ifdef CONFIG_HMEM_REPORTING
+       struct node_hmem_attrs  hmem_attrs;
+#endif
 };
 #define to_access_nodes(dev) container_of(dev, struct node_access_nodes, dev)
 
@@ -148,6 +151,62 @@ free:
        return NULL;
 }
 
+#ifdef CONFIG_HMEM_REPORTING
+#define ACCESS_ATTR(name)                                                 \
+static ssize_t name##_show(struct device *dev,                            \
+                          struct device_attribute *attr,                  \
+                          char *buf)                                      \
+{                                                                         \
+       return sprintf(buf, "%u\n", to_access_nodes(dev)->hmem_attrs.name); \
+}                                                                         \
+static DEVICE_ATTR_RO(name);
+
+ACCESS_ATTR(read_bandwidth)
+ACCESS_ATTR(read_latency)
+ACCESS_ATTR(write_bandwidth)
+ACCESS_ATTR(write_latency)
+
+static struct attribute *access_attrs[] = {
+       &dev_attr_read_bandwidth.attr,
+       &dev_attr_read_latency.attr,
+       &dev_attr_write_bandwidth.attr,
+       &dev_attr_write_latency.attr,
+       NULL,
+};
+
+/**
+ * node_set_perf_attrs - Set the performance values for given access class
+ * @nid: Node identifier to be set
+ * @hmem_attrs: Heterogeneous memory performance attributes
+ * @access: The access class the for the given attributes
+ */
+void node_set_perf_attrs(unsigned int nid, struct node_hmem_attrs *hmem_attrs,
+                        unsigned access)
+{
+       struct node_access_nodes *c;
+       struct node *node;
+       int i;
+
+       if (WARN_ON_ONCE(!node_online(nid)))
+               return;
+
+       node = node_devices[nid];
+       c = node_init_node_access(node, access);
+       if (!c)
+               return;
+
+       c->hmem_attrs = *hmem_attrs;
+       for (i = 0; access_attrs[i] != NULL; i++) {
+               if (sysfs_add_file_to_group(&c->dev.kobj, access_attrs[i],
+                                           "initiators")) {
+                       pr_info("failed to add performance attribute to node %d\n",
+                               nid);
+                       break;
+               }
+       }
+}
+#endif
+
 #define K(x) ((x) << (PAGE_SHIFT - 10))
 static ssize_t node_read_meminfo(struct device *dev,
                        struct device_attribute *attr, char *buf)

diff --git a/include/linux/node.h b/include/linux/node.h
index bb288817ed331a66f1642bb0b6f476a4c5ad016c..4139d728f8b381a158b66ea57d128c0c3520c806 100644 (file)
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -20,6 +20,32 @@
 #include <linux/list.h>
 #include <linux/workqueue.h>
 
+/**
+ * struct node_hmem_attrs - heterogeneous memory performance attributes
+ *
+ * @read_bandwidth:    Read bandwidth in MB/s
+ * @write_bandwidth:   Write bandwidth in MB/s
+ * @read_latency:      Read latency in nanoseconds
+ * @write_latency:     Write latency in nanoseconds
+ */
+struct node_hmem_attrs {
+       unsigned int read_bandwidth;
+       unsigned int write_bandwidth;
+       unsigned int read_latency;
+       unsigned int write_latency;
+};
+
+#ifdef CONFIG_HMEM_REPORTING
+void node_set_perf_attrs(unsigned int nid, struct node_hmem_attrs *hmem_attrs,
+                        unsigned access);
+#else
+static inline void node_set_perf_attrs(unsigned int nid,
+                                      struct node_hmem_attrs *hmem_attrs,
+                                      unsigned access)
+{
+}
+#endif
+
 struct node {
        struct device   dev;
        struct list_head access_list;