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(Change rejected by FESCo)
 
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<!-- The actual name of your proposed change page should look something like: Changes/Your_Change_Proposal_Name.  This keeps all change proposals in the same namespace -->
 
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= POWER 4k page size =
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= POWER 4KiB page size =
  
 
== Summary ==
 
== Summary ==
  
On ppc64le, the kernel is currently compiled for 64k page size.
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On ppc64le, the kernel is currently compiled for 64 KiB page size.
  
This change proposes using the more common 4k page size.
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This change proposes using the more common 4 KiB page size.
  
 
Some HPC workloads may be disadvantaged slightly.  Workstation users are likely to encounter fewer bugs.
 
Some HPC workloads may be disadvantaged slightly.  Workstation users are likely to encounter fewer bugs.
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[[Category:SystemWideChange]]
 
[[Category:SystemWideChange]]
  
* Targeted release: [[Releases/34 | Fedora 34 ]]  
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* Targeted release: [[Releases/35 | Fedora 35 ]]  
 
* Last updated: <!-- this is an automatic macro — you don't need to change this line -->  {{REVISIONYEAR}}-{{REVISIONMONTH}}-{{REVISIONDAY2}}  
 
* Last updated: <!-- this is an automatic macro — you don't need to change this line -->  {{REVISIONYEAR}}-{{REVISIONMONTH}}-{{REVISIONDAY2}}  
 
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CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development
 
CLOSED as NEXTRELEASE -> change is completed and verified and will be delivered in next release under development
 
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* FESCo issue: <will be assigned by the Wrangler>
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* FESCo issue: [https://pagure.io/fesco/issue/2581 #2581]
 
* Tracker bug: <will be assigned by the Wrangler>
 
* Tracker bug: <will be assigned by the Wrangler>
 
* Release notes tracker: <will be assigned by the Wrangler>
 
* Release notes tracker: <will be assigned by the Wrangler>
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== Scope ==
 
== Scope ==
* Proposal owners: [[Daniel Pocock]]
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* Proposal owners: [[DanielPocock]]
 
<!-- What work do the feature owners have to accomplish to complete the feature in time for release?  Is it a large change affecting many parts of the distribution or is it a very isolated change? What are those changes?-->
 
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<!-- Does this feature require coordination with release engineering (e.g. changes to installer image generation or update package delivery)?  Is a mass rebuild required?  include a link to the releng issue.  
 
<!-- Does this feature require coordination with release engineering (e.g. changes to installer image generation or update package delivery)?  Is a mass rebuild required?  include a link to the releng issue.  
 
The issue is required to be filed prior to feature submission, to ensure that someone is on board to do any process development work and testing and that all changes make it into the pipeline; a bullet point in a change is not sufficient communication -->
 
The issue is required to be filed prior to feature submission, to ensure that someone is on board to do any process development work and testing and that all changes make it into the pipeline; a bullet point in a change is not sufficient communication -->
 +
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** wait for 5.12 kernel, verify that it includes the Btrfs patches for arbitrary 4 KiB / 64 KiB sector size, independent of the page size
 +
** create a kernel with 4 KiB page size to run on the ppc64le build servers
 +
** ensure the default kernel RPM in the distribution has 4 KiB page size
 +
** perform the mass rebuild running on the 4 KiB page size
 +
** create an installer ISO based on the revised kernel with 4 KiB page size
 +
  
 
* Policies and guidelines: no, as it is an arch-specific issues, most other architectures already have a 4k page size <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 
* Policies and guidelines: no, as it is an arch-specific issues, most other architectures already have a 4k page size <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
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<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 
<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
N/A (not a System Wide Change)
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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 4 KiB and 64 KiB.  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@lists.fedoraproject.org/message/YSHMXGYJW5GTGF3DC7HHRYKUUT7DIVUV/].
  
 
== How To Test ==
 
== How To Test ==
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  - Green has been scientifically proven to be the most relaxing color. The move to a default background color of green with green text will result in Fedora users being the most relaxed users of any operating system.
 
  - Green has been scientifically proven to be the most relaxing color. The move to a default background color of green with green text will result in Fedora users being the most relaxed users of any operating system.
 
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-->
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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 4KiB 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 ==
 
== Dependencies ==
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<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 
<!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
N/A (not a System Wide Change)  
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All RPMs must be rebuilt on a server running the final page size (4KiB)
  
 
== Contingency Plan ==
 
== Contingency Plan ==
  
 
<!-- If you cannot complete your feature by the final development freeze, what is the backup plan?  This might be as simple as "Revert the shipped configuration".  Or it might not (e.g. rebuilding a number of dependent packages).  If you feature is not completed in time we want to assure others that other parts of Fedora will not be in jeopardy.  -->
 
<!-- If you cannot complete your feature by the final development freeze, what is the backup plan?  This might be as simple as "Revert the shipped configuration".  Or it might not (e.g. rebuilding a number of dependent packages).  If you feature is not completed in time we want to assure others that other parts of Fedora will not be in jeopardy.  -->
* Contingency mechanism: (What to do?  Who will do it?) N/A (not a System Wide Change) <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
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* Contingency mechanism: Prepare a kernel with the original 64k config, install it on the build server, rebuild all the packages for this architecture <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 
<!-- When is the last time the contingency mechanism can be put in place?  This will typically be the beta freeze. -->
 
<!-- When is the last time the contingency mechanism can be put in place?  This will typically be the beta freeze. -->
* Contingency deadline: N/A (not a System Wide Change) <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
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* Contingency deadline: whenever the last time for a full rebuild or kernel change is possible <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 
<!-- Does finishing this feature block the release, or can we ship with the feature in incomplete state? -->
 
<!-- Does finishing this feature block the release, or can we ship with the feature in incomplete state? -->
* Blocks release? N/A (not a System Wide Change), Yes/No <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
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* Blocks release? Yes, full rebuild of all packages must be completed before release <!-- REQUIRED FOR SYSTEM WIDE CHANGES -->
 
* Blocks product? product <!-- Applicable for Changes that blocks specific product release/Fedora.next -->
 
* Blocks product? product <!-- Applicable for Changes that blocks specific product release/Fedora.next -->
  

Latest revision as of 19:46, 8 March 2021


POWER 4KiB page size

Summary

On ppc64le, the kernel is currently compiled for 64 KiB page size.

This change proposes using the more common 4 KiB 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.

Owner

Current status

  • Targeted release: Fedora 35
  • Last updated: 2021-03-08
  • FESCo issue: #2581
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

Feedback

Discussed several times on devel, latest here

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

  • Other developers: please volunteer by adding your name here
  • Release engineering: #9939 (a check of an impact with Release Engineering is needed)
    • wait for 5.12 kernel, verify that it includes the Btrfs patches for arbitrary 4 KiB / 64 KiB sector size, independent of the page size
    • create a kernel with 4 KiB page size to run on the ppc64le build servers
    • ensure the default kernel RPM in the distribution has 4 KiB page size
    • perform the mass rebuild running on the 4 KiB page size
    • create an installer ISO based on the revised kernel with 4 KiB 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 4 KiB and 64 KiB. This is anticipated in a future kernel release, 5.12 and will hopefully be ready for F34 or F35[1].

How To Test

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 4KiB 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 (4KiB)

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
  • Blocks product? product

Documentation

Release Notes