On 07/01/2021 19:15, Dan Horák wrote:
On Thu, 7 Jan 2021 18:00:42 +0000
Peter Robinson <pbrobinson(a)gmail.com> wrote:
> On Thu, Jan 7, 2021 at 3:24 PM Neal Gompa <ngompa13(a)gmail.com> wrote:
>> On Thu, Jan 7, 2021 at 10:10 AM Daniel Pocock <daniel(a)pocock.pro> wrote:
>>> On 07/01/2021 12:35, Dan Horák wrote:
>>>> Hi Daniel,
>>>> On Wed, 6 Jan 2021 14:11:37 +0100
>>>> Daniel Pocock <daniel(a)pocock.pro> wrote:
>>>>> We did some more troubleshooting of AMD Radeon issues on ppc64
>>>>> As with Nouveau, it looks like a change from 64k to 4k page size got
>>>>> working again with RX 5700. I suspect it will be similar for RX 6800
>>>>> we can get some of them, they are a good complement for the compute
>>>>> The issue is page size, not ppc64
>>>> are you talking about Maurizio's issue? When I was talking with the
>>>> who fixed the Navi 10 driver for Power, he wasn't aware of any page
>>>> size issues. But it sounds plausible.
>>> Yes, it is in the Raptor forum
>>> To save reading, I gave him the following in an apt repository:
>>> - 5.9.6 kernel with 4k page size
>>> - mesa 20.3
>>> - deps for mesa (llvm-11, libdrm, ...)
>>> He took the 2020-10-22 firmware snapshot from Debian unstable
>>> He disabled Wayland, to use Xorg
>>> It worked.
>>> I'm hoping that exactly the same set of packages will work for me
>>> whenever I can get my hands on an RX 6800 XT card.
>>> As mentioned elsewhere in this thread and in various parts of the Raptor
>>> forum, especially this thread, there are a range of applications
>>> where page size appears to have some impact.
>>> I'd like to emphasize that there are a range of issues where page size
>>> does not appear to be a factor, there are a backlog of these issues.
>>> Therefore, emphasizing this quite strongly, I feel it is better for
>>> people to run 4k page size on workstations from F-34 so we can clearly
>>> flush out the PPC issues on 4k before we even begin to address issues
>>> with 64k. As examples, I have issues with Blender, Firefox and
>>> JPEGs in OBS where page size has been eliminated but I also have
>>> another issue with Firefox, or maybe v4l2-loopback, where page size
>>> is a factor.
>>> Vikings and Raptor hope to sell a lot more of these systems when they go
>>> live in 2021. Vikings in particular has put great effort into a
>>> German-engineering water cooling solution, there is a leaked photo in
>>> the Raptor forum. Personally, I already identified the traps in this
>>> platform within hours of unboxing but I know a lot of the users,
>>> including Fedora users, will benefit from a slightly softer landing on
>>> POWER9. I can't personally spend time following every issue through to
>>> completion myself (unless somebody wants to offer me a bounty) but I try
>>> to document them as well as I can both here and in the bug trackers.
>> You could make a Change proposal to switch Fedora on POWER back to 4k
>> page sizes. Or just talk to the Fedora kernel maintainers about
>> switching it back. We did this four years ago for ARM (as Peter
>> noted), and if it really continues to be a problem for desktop
>> POWER systems, then switching back makes sense.
> The arm team made that change by engaging with all the people that
> would be impacted after working with the toolchain teams to ensure the
> userspace had all the needed fixes to ensure it was purely a kernel
> config change, that was around 18 months work to get to that point
> (yes, and POWER64 likely benefits from that ~ 10 releases later) but
> the likes of IBM should be engaged because they obviously also have an
> interest and are active users/contributors of Fedora on POWER.
I'm talking with them,
Can Fedora ship multiple flavours from a single source package of the
kernel, as in Debian? This doesn't solve the issue of ensuring every
other package in the archive is rebuilt on a host with the same page
size, but it puts the 4k kernel within reach for many more people. In
my case, it allowed me to "divide and conquer", probably not the best
metaphor to use this week, but nonetheless, it allowed me to sideline
the page size issues and focus on other issues.
If Fedora can ship both 64k and 4k kernel with an easy way for users to
alternate between them, that could be a middle ground for F-34.
Going completely 4k or completely fixing 64k, either of these directions
requires an effort now. I can see some hope though:
- can strace or some other mechanism be used during userspace package
builds to see which packages are calling getconf(PAGESIZE / PAGE_SIZE)
from their Makefiles, excluding the unit tests?
- can reproducible builds methods be used to compare userspace packages
built on both 4k and 64k to try and work out which packages are built
IBM already offered some bounties for work on POWER. There are a number
of people who may be willing to contribute to parts of this effort if
incentives can be aligned with their projects. If IBM can make the
hardware more accessible, like the Lenovo offers for developers, that
could also encourage people.