5:55 a.m.
Le 08/04/2019 à 16:56, Dan Williams a écrit :
Yes, I agree with all of the above, but I think we need a way to fix
this independent of the HMAT data being present. The SLIT already
tells the kernel enough to let tooling figure out equidistant "local"
nodes. While the numa_node attribute will remain a singleton the
tooling needs to handle this case and can't assume the HMAT data will
be present.
So you want to export the part of SLIT that is currently hidden to
userspace because the corresponding nodes aren't registered?
With the patch below, I get 17 17 28 28 in dax0.0/node_distance which
means it's close to node0 and node1.
The code is pretty much a duplicate of read_node_distance() in
drivers/base/node.c. Not sure it's worth factorizing such small functions?
The name "node_distance" (instead of "distance" for NUMA nodes) is
also
subject to discussion.
Brice
commit 6488b6a5c942a972b97c2f28d566d89b9917ef1d
Author: Brice Goglin <Brice.Goglin(a)inria.fr>
Date: Mon Apr 8 21:44:30 2019 +0200
device-dax: Add a 'node_distance' attribute
This attribute is identical to the 'distance' attribute
inside NUMA node directories. It lists the distance
from the DAX device to each online NUMA node.
Signed-off-by: Brice Goglin <Brice.Goglin(a)inria.fr>
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 2109cfe80219..35a80c852e0d 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -295,6 +295,28 @@ static ssize_t target_node_show(struct device *dev,
}
static DEVICE_ATTR_RO(target_node);
+static ssize_t node_distance_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct dev_dax *dev_dax = to_dev_dax(dev);
+ int nid = dev_dax_target_node(dev_dax);
+ int len = 0;
+ int i;
+
+ /*
+ * buf is currently PAGE_SIZE in length and each node needs 4 chars
+ * at the most (distance + space or newline).
+ */
+ BUILD_BUG_ON(MAX_NUMNODES * 4 > PAGE_SIZE);
+
+ for_each_online_node(i)
+ len += sprintf(buf + len, "%s%d", i ? " " : "",
node_distance(nid, i));
+
+ len += sprintf(buf + len, "\n");
+ return len;
+}
+static DEVICE_ATTR(node_distance, S_IRUGO, node_distance_show, NULL);
+
static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
@@ -320,6 +342,7 @@ static struct attribute *dev_dax_attributes[] = {
&dev_attr_modalias.attr,
&dev_attr_size.attr,
&dev_attr_target_node.attr,
+ &dev_attr_node_distance.attr,
NULL,
};