[Bug 270943] Complete system freeze on Asus dual socket AMD 7742 system

From: <bugzilla-noreply_at_freebsd.org>
Date: Mon, 24 Apr 2023 17:59:52 UTC

--- Comment #2 from Neil Bradley <nb@synthcom.com> ---
Workaround for this is to go in to BIOS, select "AMD CBS", then "Processor
Features", and change "Global C state control" to "enabled" (or disabled, but
this uses more power). "auto" Is the setting that seems to cause the lockups.
Once changed to enabled or disabled, the system is stable for >12 hours.

More detail, with C state control "disabled", I get the following wattage

Power in  = 300 watts
Power out = 276 watts
CPU       = 168 watts
Mem       = 112 watts

root@amd-megaserver:/home/nb # sysctl dev.cpu | grep cx
dev.cpu.255.cx_method: C1/hlt
dev.cpu.255.cx_usage_counters: 2525
dev.cpu.255.cx_usage: 100.00% last 713773us
dev.cpu.255.cx_lowest: C1
dev.cpu.255.cx_supported: C1/1/0

However, when running with C state control "enabled", it's much more reasonable
and in line with other operating systems' idle power consumption:

Power in  = 120 watts
Power out = 108 watts
CPU       = 88 watts
Mem       = 16 watts

nb@amd-megaserver:~ $ sysctl dev.cpu | grep cx
dev.cpu.255.cx_method: C1/hlt C2/io
dev.cpu.255.cx_usage_counters: 1752 0
dev.cpu.255.cx_usage: 100.00% 0.00% last 395716us
dev.cpu.255.cx_lowest: C1
dev.cpu.255.cx_supported: C1/1/1 C2/2/400

Unsure of how to properly disposition this, as while this does provide a usable
workaround, it does feel like there's something OS-wise that's not quite right,
given there are no lockup issues with Linux or Windows.

Leaving open for the FreeBSD to disposition as they see fit with the
information above.

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