Commit e1cf33aa authored by Keith Busch's avatar Keith Busch Committed by Greg Kroah-Hartman
Browse files

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: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
Reviewed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarBrice Goglin <Brice.Goglin@inria.fr>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 08d9dbe7

Documentation/ABI/stable/sysfs-devices-node

+28 −0
Original line number Diff line number Diff line
@@ -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.

drivers/base/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -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

drivers/base/node.c

+59 −0
Original line number Diff line number Diff line
@@ -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)

include/linux/node.h

+26 −0
Original line number Diff line number Diff line
@@ -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;

CRA Git | Maintained and supported by SUSTech CRA and CCSE