On Fri, 12 Feb 2021 11:20:21 -0500 Ben Cotton <bcotton@xxxxxxxxxx> wrote: > https://fedoraproject.org/wiki/Changes/Power4kPageSize > > == Summary == > > On ppc64le, the kernel is currently compiled for 64k page size. > > This change proposes using the more common 4k page size. > > Some HPC workloads may be disadvantaged slightly. Workstation users > are likely to encounter fewer bugs. > > Some things, like the AMD Radeon GPU drivers, firmware or related > code, appear to be completely non-functional on the 64k page size. > Insufficient upstream developers are testing such issues on this > architecture. as usually there are benefits and drawbacks for both the 64k and 4k page sizes. I have been gathering some additional feedback through other channels. The resulting feedback is that 4k pages will or might hit some limitations or untested features in memory allocation algorithms, in the virtual machine management space (HPT vs radix, huge tables, etc), in server features like PMDK or in IO/interrupt management. On the other hand the feedback from other distros running with 4k page is positive. So from a desktop/workstation user perspective going to 4k should be OK. Tom mentions later in this thread small or no activity in the community on further debugging or bisecting of the reported problems from 64k systems. I agree it's not good, but being able to provide such information to the developers requires both some knowledge and hardware (and time too). Due to the limited community size it might be difficult to get all those factors at the same time. I have some ideas how to improve this, but the various levels of lockdowns across the world don't make things like lab accesses easy. The open question still is whether we should try to keep 64k as default as it would allow to find the remaining bugs and offer 4k kernel variant (COPR for ppc64le should be coming back soon), similar for the installer (a new remix/spin). After BTRFS removes the page size dependency, switching the kernels shouldn't cause any issues for users. Dan > == Owner == > * Name: [[User:pocock|Daniel Pocock]] > * Email: daniel@xxxxxxxxxx > > > == Detailed Description == > > > == Feedback == > Discussed several times on devel, > [https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx/thread/3ZBQBUN67RG6U5QHOTBHEXAKR77S3NIC/ > latest here] > > [https://forums.raptorcs.com/index.php/topic,248.msg1852.html > discussed upstream in the Raptor forum] > > == Benefit to Fedora == > Better first impression for users of ppc64le workstations. > > Users can focus on reporting ppc64le bugs without being sidetracked by > page size bugs. > > == Scope == > * Proposal owners: [[DanielPocock]] > * Other developers: please volunteer by adding your name here > > * Release engineering: [https://pagure.io/releng/issue/9939 #9939] > ** wait for 5.12 kernel, verify that it includes the Btrfs patches for > arbitrary 4k / 64k sector size, independent of the page size > ** create a kernel with 4k page size to run on the ppc64le build servers > ** ensure the default kernel RPM in the distribution has 4k page size > ** perform the mass rebuild running on the 4k page size > ** create an installer ISO based on the revised kernel with 4k page size > > * Policies and guidelines: no, as it is an arch-specific issues, most > other architectures already have a 4k page size > * Trademark approval: N/A (not needed for this Change) > * Alignment with Objectives: none of the current objectives relate to > this change > > > == Upgrade/compatibility impact == > If the user has already formatted their root filesystem with Btrfs and > a 64k sector size, they need to be using a Fedora kernel that supports > both 4k and 64k. This is anticipated in a future kernel release, 5.12 > and will hopefully be ready for F34 or > F35[https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx/message/YSHMXGYJW5GTGF3DC7HHRYKUUT7DIVUV/]. > > > == User Experience == > New GPUs are more likely to just work on this non-x86 architecture, as > long as the latest firmware, mesa, llvm are also used. > > Btrfs, the default filesystem, will use the sector size identical to > the running kernel's page size. As the 4k page size is more common, > this will ensure Btrfs filesystems created on ppc64le hosts can be > used on x86 and other hosts without hassle. > > == Dependencies == > All RPMs must be rebuilt on a server running the final page size (4k) > > == Contingency Plan == > * Contingency mechanism: Prepare a kernel with the original 64k > config, install it on the build server, rebuild all the packages for > this architecture > * Contingency deadline: whenever the last time for a full rebuild or > kernel change is possible > * Blocks release? Yes, full rebuild of all packages must be completed > before release > > > > > > -- > Ben Cotton > He / Him / His > Senior Program Manager, Fedora & CentOS Stream > Red Hat > TZ=America/Indiana/Indianapolis > _______________________________________________ > devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx > To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx > Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines > List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx > Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
