linux-kernel - Re: [PATCH] drivers/base/node.c: export physical address range of given node (Re: NUMA node information for pages)

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Message-ID: <alpine.DEB.2.02.1404110325210.30610@chino.kir.corp.google.com>
Date:	Fri, 11 Apr 2014 04:00:20 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
cc:	drepper@...il.com, anatol.pomozov@...il.com, jkosina@...e.cz,
	akpm@...ux-foundation.org, xemul@...allels.com,
	paul.gortmaker@...driver.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] drivers/base/node.c: export physical address range of
 given node (Re: NUMA node information for pages)

On Thu, 10 Apr 2014, Naoya Horiguchi wrote:

> Yes, that's right, but it seems to me that just node_start_pfn and node_end_pfn
> is not enough because there can be holes (without any page struct backed) inside
> [node_start_pfn, node_end_pfn), and it's not aware of memory hotplug.
> 

So?  Who cares if there are non-addressable holes in part of the span?  
Ulrich, correct me if I'm wrong, but it seems you're looking for just a 
address-to-nodeid mapping (or pfn-to-nodeid mapping) and aren't actually 
expecting that there are no holes in a node for things like acpi or I/O or 
reserved memory.

The node spans a contiguous length of memory, there's no consideration for 
addresses that aren't actually backed by physical memory.  We are just 
representing proximity domains that have a base address and length in the 
acpi world.

Memory hotplug is already taken care of because onlining and offlining 
nodes already add these node classes and {start,end}_phys_addr would 
show up automatically.  If you use node_start_pfn(nid) and 
node_end_pfn(nid) as suggested, there's no futher consideration needed for 
hotplug.

I think trying to represent holes and handling different memory models and 
hotplug in special ways is complete overkill.

Ulrich, can I have your ack?
---
 Documentation/ABI/stable/sysfs-devices-node | 12 ++++++++++++
 drivers/base/node.c                         | 18 ++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-devices-node b/Documentation/ABI/stable/sysfs-devices-node
--- a/Documentation/ABI/stable/sysfs-devices-node
+++ b/Documentation/ABI/stable/sysfs-devices-node
@@ -63,6 +63,18 @@ Description:
 		The node's hit/miss statistics, in units of pages.
 		See Documentation/numastat.txt
 
+What:		/sys/devices/system/node/nodeX/start_phys_addr
+Date:		April 2014
+Contact:	David Rientjes <rientjes@...gle.com>
+Description:
+		The physical base address of this node.
+
+What:		/sys/devices/system/node/nodeX/end_phys_addr
+Date:		April 2014
+Contact:	David Rientjes <rientjes@...gle.com>
+Description:
+		The physical base + length address of this node.
+
 What:		/sys/devices/system/node/nodeX/distance
 Date:		October 2002
 Contact:	Linux Memory Management list <linux-mm@...ck.org>
diff --git a/drivers/base/node.c b/drivers/base/node.c
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -170,6 +170,20 @@ static ssize_t node_read_numastat(struct device *dev,
 }
 static DEVICE_ATTR(numastat, S_IRUGO, node_read_numastat, NULL);
 
+static ssize_t node_read_start_phys_addr(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "0x%lx\n", node_start_pfn(dev->id) << PAGE_SHIFT);
+}
+static DEVICE_ATTR(start_phys_addr, S_IRUGO, node_read_start_phys_addr, NULL);
+
+static ssize_t node_read_end_phys_addr(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "0x%lx\n", node_end_pfn(dev->id) << PAGE_SHIFT);
+}
+static DEVICE_ATTR(end_phys_addr, S_IRUGO, node_read_end_phys_addr, NULL);
+
 static ssize_t node_read_vmstat(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
@@ -286,6 +300,8 @@ static int register_node(struct node *node, int num, struct node *parent)
 		device_create_file(&node->dev, &dev_attr_cpulist);
 		device_create_file(&node->dev, &dev_attr_meminfo);
 		device_create_file(&node->dev, &dev_attr_numastat);
+		device_create_file(&node->dev, &dev_attr_start_phys_addr);
+		device_create_file(&node->dev, &dev_attr_end_phys_addr);
 		device_create_file(&node->dev, &dev_attr_distance);
 		device_create_file(&node->dev, &dev_attr_vmstat);
 
@@ -311,6 +327,8 @@ void unregister_node(struct node *node)
 	device_remove_file(&node->dev, &dev_attr_cpulist);
 	device_remove_file(&node->dev, &dev_attr_meminfo);
 	device_remove_file(&node->dev, &dev_attr_numastat);
+	device_remove_file(&node->dev, &dev_attr_start_phys_addr);
+	device_remove_file(&node->dev, &dev_attr_end_phys_addr);
 	device_remove_file(&node->dev, &dev_attr_distance);
 	device_remove_file(&node->dev, &dev_attr_vmstat);
 
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