[OVMF+VIFO+QEMU] Large VM RAM allocation = Long Boot Times

[OVMF+VIFO+QEMU] Large VM RAM allocation = Long Boot Times

[A Z]

This is an issue that involves a combination of different software
packages, so my apologies in advance if this is the wrong list to post on.

I'm experiencing terrible boot times when I assign a large amount of RAM to
a VM when used in combination with VIFO/PCI-passthrough.

On a VM with a Nvidia GTX 970 + USB controller and 24GiB of RAM assigned,
the time to the TianoCore splash screen is ~5 minutes. It's then ~30
seconds before Windows 10 begins to boot (spinning dots). During this time,
the QEMU CPU core threads are 100% busy.

According to `perf`, the QMU CPU core threads are spending most of their
time waiting on a spinlock over kvm->mmu_lock that's created by
kvm_zap_gfn_range.

I'm fairly certain that ~1 year ago (if not longer) the same configuration
didn't take this long to boot.

Regards,
Adam

Re: [OVMF+VIFO+QEMU] Large VM RAM allocation = Long Boot Times

[Philippe Mathieu-Daudé]

Cc'ing qemu-devel@

On 15/11/18 6:58, A Z wrote:
> This is an issue that involves a combination of different software
> packages, so my apologies in advance if this is the wrong list to post on.
> 
> I'm experiencing terrible boot times when I assign a large amount of RAM to
> a VM when used in combination with VIFO/PCI-passthrough.
> 
> On a VM with a Nvidia GTX 970 + USB controller and 24GiB of RAM assigned,
> the time to the TianoCore splash screen is ~5 minutes. It's then ~30
> seconds before Windows 10 begins to boot (spinning dots). During this time,
> the QEMU CPU core threads are 100% busy.
> 
> According to `perf`, the QMU CPU core threads are spending most of their
> time waiting on a spinlock over kvm->mmu_lock that's created by
> kvm_zap_gfn_range.
> 
> I'm fairly certain that ~1 year ago (if not longer) the same configuration
> didn't take this long to boot.
> 
> Regards,
> Adam

Re: [OVMF+VIFO+QEMU] Large VM RAM allocation = Long Boot Times

[Laszlo Ersek]

On 11/15/18 06:58, A Z wrote:
> This is an issue that involves a combination of different software
> packages, so my apologies in advance if this is the wrong list to post on.
> 
> I'm experiencing terrible boot times when I assign a large amount of RAM to
> a VM when used in combination with VIFO/PCI-passthrough.
> 
> On a VM with a Nvidia GTX 970 + USB controller and 24GiB of RAM assigned,
> the time to the TianoCore splash screen is ~5 minutes. It's then ~30
> seconds before Windows 10 begins to boot (spinning dots). During this time,
> the QEMU CPU core threads are 100% busy.
> 
> According to `perf`, the QMU CPU core threads are spending most of their
> time waiting on a spinlock over kvm->mmu_lock that's created by
> kvm_zap_gfn_range.
> 
> I'm fairly certain that ~1 year ago (if not longer) the same configuration
> didn't take this long to boot.

I see you posted this to vfio-users as well -- that would have been my
recommendation anyway. I'll follow up there briefly.

Thanks
Laszlo