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Re: [vfio-users] Eliminate Mini Stutter in "Witcher 3: The Wild Hunt" on top of KVM/VFIO



On Tue, Mar 15, 2016 at 10:25 PM, Okky Hendriansyah <okky htf gmail com> wrote:
Hi All,

I experienced a very noticeable mini stutters here and there when playing "Witcher 3: The Wild Hunt" on my Windows 10 VM with OVMF and MSI enabled. I was using the official linux-lts-4.1.19-1 from Arch Linux repository. Apparently after changing these 3 kernel configurations and recompile the kernel, the mini stutter issues are gone!

Here are the kernel configuration that I changed:
1.) 1000 MHz clock resolution
2.) Voluntary preemption scheduling
3.) Madvise hugepages (not really sure that this changes anything actually)

I am not really sure whether all or just one of them specifically eliminate the mini stuttering. If someone had any idea what is really going on, my ears are open. I found the kernel config changes from nbhs' early post [1] and since my VM disk is on ZFS  [2].

The Fedora kernel already sets all of these, however regarding 3) the advice from nbhs is to use hugetlbfs and not rely on transparent hugepages.  Transparent hugepages is not compatible with device assignment since pages get pinned as the VM is created, there's no opportunity for transparent hugepages to take effect.  Therefore I don't think your madvise change is doing anything.

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