[vfio-users] [FEEDBACK NEEDED] Additionnal tips to include in the Arch wiki article

[Okky Hendriansyah]

On Tue, May 10, 2016 at 12:55 AM, Alex Williamson <
alex.l.williamson at gmail.com> wrote:

> On Mon, May 9, 2016 at 11:13 AM, Okky Hendriansyah <okky.htf at gmail.com>
> wrote:
>
>>
>> Appreciate your work on this. I would like to propose other things about
>> VFIO/OVMF GPU passthrough that in my opinion should be included in the wiki
>> as well:
>>
>> 1.) Avoid transparent hugepages and enable explicit hugepages (hugepages
>> size variance 2 MB, 1 GB)
>>
>
> Not sure whether you're talking about the current THP bug or simply that
> THP is not useful for device assignment.  The bug will be fixed soon enough
> and adding it to a wiki is probably just going to make it last longer than
> it needs to.
>

I was referring to the latter one that THP is not really useful for device
assignment and in general using explicit hugepages gives more performance
benefit for QEMU process. Also since currently virt-manager did not have
graphical representation of the option, mentioning how to add it into the
XML file would benefit new users how to incorporate that into their setup.


> 2.) Kernel configuration to improve performance like 1000 Hz clock
>> resolution, Voluntary Preemptible Kernel, halt_poll_ns
>>
>
> halt_poll_ns already has a stable backport to turn it down to a value that
> doesn't behave as poorly.  Seems like another issue that's going to be gone
> before too long.
>

I noticed that some recent kernel versions had their default values for
halt_poll_ns turned down to 400000. But not all of us run the latest and
greatest kernel version for one reason or the other. Similar the part of
the wiki that tells abous legacy way to isolating the GPU by using
pci-stub, it just gives alternatives on how new users can do it. Probably
the more relevant section is about which kernel versions to avoid in order
to not experiencing weird behaviors like in kernel 4.2.x and 4.3.x.

Best regards,
Okky Hendriansyah
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