linux-cachyos-rc: Use lazy preemption by default #373
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By observing a few results, it is observed that dynamic preemption can somehow blur the results between the various preemption models. One example is [1] where there seems to be a 5% difference in throughput between voluntary vs full with dynamic preemption disabled but then the difference goes to a measly 0.6% when dynamic preemption is enabled. I've also been able to reproduce this behaviour across various benchmarks, one of them shared in [2]. Due to that, let's disable dynamic preemption for all kernel configurations (or atleast the default). Note that PREEMPT_DYNAMIC is kept enabled for fully preempted kernels, as it is observed that it doesn't seem to matter for those, so having more options is the priority in this case. [1] https://lore.kernel.org/all/[email protected]/ [2] #339 Signed-off-by: Eric Naim <[email protected]>
With promising results shared in #339, let's enable this and see how it goes. Signed-off-by: Eric Naim <[email protected]>
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https://flightlesssomething.ambrosia.one/benchmark/950 New evidence has shown that lazy preemption is not meant for high CPU load responsiveness. I'm closing this PR as the config changes aren't necessary at all (modifying the config switches are sufficient). I'll consider picking them up again in the 6.13 stable sync. Note: The 650FPS average of BORE-lazy is misleading. A more accurate average would be around 350. |
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With promising results shared in #339, let's enable this and see how
it goes. A prerequisite of this is to disable dynamic preemption, which this PR already does. Further testing can be done with kernels from [1].
The last commit introduces dynamic preempt as an option in the PKGBUILD because it has been disabled by default, but I'm not too sure if we should really add this (hence it's the last commit).Dropped and left dynamic preemption enabled for fully preempted kernels.[1] https://share.cachyos.org/x86_64_v3/kernel/preempt/
Closes #339