linux-kernel - RE: [PATCH] EDAC: Expose node link in sysfs if CONFIG

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Message-ID: <SJ1PR11MB60831CF4AC4E4C23DE362E0DFC799@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Tue, 16 May 2023 17:25:49 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>, Yajun Deng <yajun.deng@...ux.dev>
CC:     "james.morse@....com" <james.morse@....com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "rric@...nel.org" <rric@...nel.org>,
        "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: RE: [PATCH] EDAC: Expose node link in sysfs if CONFIG_NUMA

>> If we have '/sys/devices/system/node/node0/mc0', by comparing the number
>> of dimm and MemTotal in meminfo. It is easy to know that the dimm didn't 
>> recognized whether it belonged to this NUMA node or not.
>
> mc != NUMA node.

Modern systems have multiple memory controllers per socket.
On an Icelake server I see:

$ cd /sys/devices/system/edac/mc
$ ls -l
total 0
drwxr-xr-x. 5 root root    0 May 16 10:13 mc0
drwxr-xr-x. 3 root root    0 May 16 10:13 mc1
drwxr-xr-x. 5 root root    0 May 16 10:13 mc2
drwxr-xr-x. 3 root root    0 May 16 10:13 mc3
drwxr-xr-x. 5 root root    0 May 16 10:13 mc4
drwxr-xr-x. 3 root root    0 May 16 10:13 mc5
drwxr-xr-x. 5 root root    0 May 16 10:13 mc6
drwxr-xr-x. 3 root root    0 May 16 10:13 mc7
drwxr-xr-x. 2 root root    0 May 16 10:13 power
lrwxrwxrwx. 1 root root    0 May 16 03:11 subsystem -> ../../../../bus/edac
-rw-r--r--. 1 root root 4096 May 16 03:11 uevent

But I can figure out the socket topology with:

$ grep . mc*/mc_name
mc0/mc_name:Intel_10nm Socket#0 IMC#0
mc1/mc_name:Intel_10nm Socket#0 IMC#1
mc2/mc_name:Intel_10nm Socket#0 IMC#2
mc3/mc_name:Intel_10nm Socket#0 IMC#3
mc4/mc_name:Intel_10nm Socket#1 IMC#0
mc5/mc_name:Intel_10nm Socket#1 IMC#1
mc6/mc_name:Intel_10nm Socket#1 IMC#2
mc7/mc_name:Intel_10nm Socket#1 IMC#3

I think this should help connect "mc*" to which node
they belong to.

-Tony