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Date: Thu, 14 Mar 2019 00:15:56 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Keith Busch <keith.busch@...el.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
Linux Memory Management List <linux-mm@...ck.org>,
Linux API <linux-api@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Rafael Wysocki <rafael@...nel.org>,
Dave Hansen <dave.hansen@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
Jonathan Cameron <jonathan.cameron@...wei.com>,
Brice Goglin <Brice.Goglin@...ia.fr>
Subject: Re: [PATCHv8 05/10] node: Add heterogenous memory access attributes
On Mon, Mar 11, 2019 at 9:55 PM Keith Busch <keith.busch@...el.com> wrote:
>
> 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@...wei.com>
> Tested-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Keith Busch <keith.busch@...el.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> Documentation/ABI/stable/sysfs-devices-node | 28 ++++++++++++++
> drivers/base/Kconfig | 8 ++++
> drivers/base/node.c | 59 +++++++++++++++++++++++++++++
> include/linux/node.h | 26 +++++++++++++
> 4 files changed, 121 insertions(+)
>
> diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node
> index 433bcc04e542..735a40a3f9b2 100644
> --- a/Documentation/ABI/stable/sysfs-devices-node
> +++ b/Documentation/ABI/stable/sysfs-devices-node
> @@ -114,3 +114,31 @@ Contact: Keith Busch <keith.busch@...el.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@...el.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@...el.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@...el.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@...el.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 059700ea3521..a7438a58c250 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -149,6 +149,14 @@ 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 6f4097680580..2de546a040a5 100644
> --- 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 @@ static struct node_access_nodes *node_init_node_access(struct node *node,
> 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 bb288817ed33..4139d728f8b3 100644
> --- 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;
> --
> 2.14.4
>
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