Re: Ryzen 4000 (Mobile) Softlocks/Micro-stutters

[Dylanger Daly <dylangerdaly@xxxxxxxxxxxxxx>]

> Does booting with sched=credit alter the symptoms?

Indeed I've tried this, the result is an observable delay, unusable performance, credit2 seems to be the only usable scheduler, I'm certain it has something to do with SMT being disabled, resulting in 8 cores instead of the expected 16 threads.

> As a random thought, have you tried disabling use of (deep) C-states?

Yeah I've tried both `processor.max_cstate=1|5`

I've also tried adding `0xC0010292` and `0xC0010296` MSRs into arch/x86/msr.c (guest_{rdmsr,wrmsr})

The above allowed me to use https://github.com/r4m0n/ZenStates-Linux/blob/master/zenstates.py

After removing `dom0_max_vcpus=1 dom0_vcpus_pin` from Xen's CMDLINE, and disabling C6 I observed no change.

> This wants reporting (with sufficient data, i.e. at least a serial log)

Hm, I'm not sure there's UART on this Laptop, can I save the boot log somewhere?

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, October 15th, 2020 at 10:57 PM, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:

On 15/10/2020 01:38, Dylanger Daly wrote:

Hi All,

I'm currently using Xen 4.14 (Qubes 4.1 OS) on a Ryzen 7 4750U PRO, by default I'll experience softlocks where the mouse for example will jolt from time to time, in this state it's not usable.

Adding `dom0_max_vcpus=1 dom0_vcpus_pin` to Xen's CMDLINE results in no more jolting however performance isn't what it should be on an 8 core CPU, softlocks are still a problem within domU's, any sort of UI animation for example.

Reverting this commit (8e2aa76dc1670e82eaa15683353853bc66bf54fc) results in even worse performance with or without the above changes to CMDLINE, and it's not usable at all.

Does anyone have any pointers?

Does booting with sched=credit alter the symptoms?

~Andrew