Software > Operating Systems and Porting
Fedora 35 (was F-34): going to 4k page size? Help needed
pocock:
Personally, I'm curious about the possibilities with 64k but I think the platform will get more momentum with 4k over the next 2-3 years. Any way to offer both would be good.
Notice that:
a) 4k kernel needs to be in the installer ISO image, if you build a kernel with Copr, you need to build an installer image too
b) all packages need to be recompiled using the 4k kernel, although I suspect less than 1% of packages will be sensitive to page size, doing a full rebuild is the only way to be sure
If anybody can add details to the thread in Fedora devel that is the best place to discuss it now
q66:
what? this makes no sense
you don't need to recompile *any* packages, since source code can't know the page size ahead of time
even if something hardcodes page size, a recompilation will not help you (not to mention that things compiled with a 64KiB page size constant will work on both 64k and 4k kernels)
pocock:
There are a small number of packages that are sensitive like this
Some comments in this thread:
https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/AAXJFZNIRXK2WRHZVYD3RUGQGZEYUH74/
and here
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=775788#15
q66:
i don't see how that's relevant
1) recompilation gives you the same binary regardless of the kernel you are running
2) therefore, if you have stuff sensitive to page size, you have to identify and patch the specific packages
3) again, things that assume 64k generally work on both 4k and 64k, so there is no problem, it's only a problem the other way around
q66:
--- Quote from: ClassicHasClass on January 08, 2021, 05:12:28 pm ---I see sharkcz is already involved in this conversation. I personally am not aware of anything that would break as a result (in fact, as you correctly point out, many things would suddenly "just work"). My only hesitancy is it would make 64K page kernels more of a pariah than they are already, sort of like another situation with big-endian, and there are performance reasons for 64K pages. Might this, perhaps, be a Workstation-only change and keep the performance benefits for Fedora Server?
--- End quote ---
i'd rather see 64k just go away
the traditional page size for powerpc is 4KiB, large default pages just have more drawbacks than benefits and i'd be surprised if you could find me a single benchmark where larger pages give you performance benefits that you can't also get by using hugepages (ideally with madvise) while retaining all the benefits of smaller pages in the general case
also https://yarchive.net/comp/linux/page_sizes.html
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