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Date: Tue, 20 Oct 2009 20:55:58 +0900 (JST)
From: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To: "Alex Chiang" <achiang@...com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
"Ingo Molnar" <mingo@...e.hu>, "Gary Hade" <garyhade@...ibm.com>,
"Badari Pulavarty" <pbadari@...ibm.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] mm: add numa node symlink for memory section in
sysfs
Alex Chiang wrote:
> Commit c04fc586c (mm: show node to memory section relationship with
> symlinks in sysfs) created symlinks from nodes to memory sections, e.g.
>
> /sys/devices/system/node/node1/memory135 -> ../../memory/memory135
>
> If you're examining the memory section though and are wondering what
> node it might belong to, you can find it by grovelling around in
> sysfs, but it's a little cumbersome.
>
> Add a reverse symlink for each memory section that points back to the
> node to which it belongs.
>
> Cc: Gary Hade <garyhade@...ibm.com>
> Cc: Badari Pulavarty <pbadari@...ibm.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Signed-off-by: Alex Chiang <achiang@...com>
2 yeas ago, I wanted to add this symlink. But don't...because
some vendor's host has no 1-to-1 relationship between a memsection
and a node. (I don't remember precisely, sorry....s390?)
Then, a memsection can be under prural nodes.
At brief look, this patch provides 1-to-1 relationship between them.
If it's ok for all stake-holders, I welcome this.
Thanks,
-Kame
> ---
>
> Documentation/ABI/testing/sysfs-devices-memory | 14 +++++++++++++-
> Documentation/memory-hotplug.txt | 11 +++++++----
> drivers/base/node.c | 11 ++++++++++-
> 3 files changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-devices-memory
> b/Documentation/ABI/testing/sysfs-devices-memory
> index 9fe91c0..bf1627b 100644
> --- a/Documentation/ABI/testing/sysfs-devices-memory
> +++ b/Documentation/ABI/testing/sysfs-devices-memory
> @@ -60,6 +60,19 @@ Description:
> Users: hotplug memory remove tools
> https://w3.opensource.ibm.com/projects/powerpc-utils/
>
> +
> +What: /sys/devices/system/memoryX/nodeY
> +Date: October 2009
> +Contact: Linux Memory Management list <linux-mm@...ck.org>
> +Description:
> + When CONFIG_NUMA is enabled, a symbolic link that
> + points to the corresponding NUMA node directory.
> +
> + For example, the following symbolic link is created for
> + memory section 9 on node0:
> + /sys/devices/system/memory/memory9/node0 -> ../../node/node0
> +
> +
> What: /sys/devices/system/node/nodeX/memoryY
> Date: September 2008
> Contact: Gary Hade <garyhade@...ibm.com>
> @@ -70,4 +83,3 @@ Description:
> memory section directory. For example, the following symbolic
> link is created for memory section 9 on node0.
> /sys/devices/system/node/node0/memory9 -> ../../memory/memory9
> -
> diff --git a/Documentation/memory-hotplug.txt
> b/Documentation/memory-hotplug.txt
> index bbc8a6a..57e7e9c 100644
> --- a/Documentation/memory-hotplug.txt
> +++ b/Documentation/memory-hotplug.txt
> @@ -160,12 +160,15 @@ Under each section, you can see 4 files.
> NOTE:
> These directories/files appear after physical memory hotplug phase.
>
> -If CONFIG_NUMA is enabled the
> -/sys/devices/system/memory/memoryXXX memory section
> -directories can also be accessed via symbolic links located in
> -the /sys/devices/system/node/node* directories. For example:
> +If CONFIG_NUMA is enabled the memoryXXX/ directories can also be accessed
> +via symbolic links located in the /sys/devices/system/node/node*
> directories.
> +
> +For example:
> /sys/devices/system/node/node0/memory9 -> ../../memory/memory9
>
> +A backlink will also be created:
> +/sys/devices/system/memory/memory9/node0 -> ../../node/node0
> +
> --------------------------------
> 4. Physical memory hot-add phase
> --------------------------------
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 1fe5536..3108b21 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -268,6 +268,7 @@ static int get_nid_for_pfn(unsigned long pfn)
> /* register memory section under specified node if it spans that node */
> int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
> {
> + int ret;
> unsigned long pfn, sect_start_pfn, sect_end_pfn;
>
> if (!mem_blk)
> @@ -284,9 +285,15 @@ int register_mem_sect_under_node(struct memory_block
> *mem_blk, int nid)
> continue;
> if (page_nid != nid)
> continue;
> - return sysfs_create_link_nowarn(&node_devices[nid].sysdev.kobj,
> + ret = sysfs_create_link_nowarn(&node_devices[nid].sysdev.kobj,
> &mem_blk->sysdev.kobj,
> kobject_name(&mem_blk->sysdev.kobj));
> + if (ret)
> + return ret;
> +
> + return sysfs_create_link_nowarn(&mem_blk->sysdev.kobj,
> + &node_devices[nid].sysdev.kobj,
> + kobject_name(&node_devices[nid].sysdev.kobj));
> }
> /* mem section does not span the specified node */
> return 0;
> @@ -315,6 +322,8 @@ int unregister_mem_sect_under_nodes(struct
> memory_block *mem_blk)
> continue;
> sysfs_remove_link(&node_devices[nid].sysdev.kobj,
> kobject_name(&mem_blk->sysdev.kobj));
> + sysfs_remove_link(&mem_blk->sysdev.kobj,
> + kobject_name(&node_devices[nid].sysdev.kobj));
> }
> return 0;
> }
>
> --
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