From 08d9dbe72b1f899468b2b34f9309e88a84f440f2 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Mon, 11 Mar 2019 14:56:00 -0600 Subject: node: Link memory nodes to their compute nodes 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. Reviewed-by: Jonathan Cameron Signed-off-by: Keith Busch Reviewed-by: Rafael J. Wysocki Tested-by: Brice Goglin Signed-off-by: Greg Kroah-Hartman --- Documentation/ABI/stable/sysfs-devices-node | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) (limited to 'Documentation') diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node index 3e90e1f3bf0a..433bcc04e542 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 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 +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 +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/accessY/targets/ +Date: December 2018 +Contact: Keith Busch +Description: + The directory containing symlinks to memory targets that + this initiator node has class "Y" access. -- cgit v1.2.3