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Tasklist

FS#75456 - [linux-lts] enable PREEMPT_DYNAMIC like the linux package to allow configuring preemption mode

Attached to Project: Arch Linux
Opened by Daniel Micay (thestinger) - Saturday, 30 July 2022, 09:17 GMT
Last edited by Andreas Radke (AndyRTR) - Thursday, 11 August 2022, 14:08 GMT
Task Type Feature Request
Category Packages: Core
Status Closed
Assigned To Andreas Radke (AndyRTR)
Architecture All
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 2
Private No

Details

CONFIG_PREEMPT_DYNAMIC=y is available since Linux 5.12 and is used for the linux package already. It allows the system administrator to choose preempt=none|voluntary|full on the kernel line. Enabling CONFIG_PREEMPT_DYNAMIC=y is a clear all around benefit allowing system administrators to choose the best mode for their use case.

The default could be left at preempt=none since linux-lts is more server focused. I don't have much of an opinion on whether it should be consistent with the linux package (preempt=full), a balanced choice (preempt=voluntary) or solely throughput focused (preempt=none) as it is now.
This task depends upon

Closed by  Andreas Radke (AndyRTR)
Thursday, 11 August 2022, 14:08 GMT
Reason for closing:  Deferred
Comment by Andreas Radke (AndyRTR) - Thursday, 11 August 2022, 14:08 GMT
Full dynamic PREEMPT support got introduced in 5.16 (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c597bfddc9e9e8a63817252b67c3ca0e544ace26)

So it's not possible in 5.15.x to have either desired CONFIG_PREEMPT_NONE=y or CONFIG_PREEMPT_VOLUNTARY=y with dynamic support.
And default CONFIG_PREEMPT=y (low latency desktop) is not desired for LTS kernels.

Please come back to me if I miss it when we move to a newer longterm branch.

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