linux-kernel - Re: [PATCH] Raise maximum number of memory controllers

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Date:   Wed, 26 Sep 2018 16:02:57 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Russ Anderson <rja@....com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Justin Ernst <justin.ernst@....com>, russ.anderson@....com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        Aristeu Rozanski Filho <arozansk@...hat.com>
Subject: Re: [PATCH] Raise maximum number of memory controllers

This issue has made me look a bit more at what EDAC puts in sysfs.
It seems like the current code inherits some useless baggage
from the device calls it makes.

E.g. all the "power" subdirectories:

$ find /sys/devices/system/edac -name power
/sys/devices/system/edac/power
/sys/devices/system/edac/mc/mc6/dimm3/power
/sys/devices/system/edac/mc/mc6/power
/sys/devices/system/edac/mc/mc6/csrow0/power
/sys/devices/system/edac/mc/mc6/dimm6/power
/sys/devices/system/edac/mc/mc6/dimm0/power
/sys/devices/system/edac/mc/mc6/dimm9/power
/sys/devices/system/edac/mc/mc4/dimm3/power
/sys/devices/system/edac/mc/mc4/power
... total of 50 of these ...

$ grep -r . /sys/devices/system/edac/mc/mc6/dimm0/power
/sys/devices/system/edac/mc/mc6/dimm0/power/runtime_active_time:0
/sys/devices/system/edac/mc/mc6/dimm0/power/runtime_status:unsupported
grep: /sys/devices/system/edac/mc/mc6/dimm0/power/autosuspend_delay_ms: Input/output error
/sys/devices/system/edac/mc/mc6/dimm0/power/runtime_suspended_time:0
/sys/devices/system/edac/mc/mc6/dimm0/power/control:auto

We don't have stats, nor control of power on a per memory controller
or per dimm basis. So all these files are just noise.

But ... we are at -rc5. Not sure that we'll figure out, write, test & debug
the proper solution in the next 3-4 weeks. So perhaps we should apply

-#define EDAC_MAX_MCS   16
+#define EDAC_MAX_MCS   64

as a temporary band-aid to get HPE's 32-socket machine running while
we work on the proper fix?

-Tony