Apply rt kernel patch to linux 4 4 2 #401
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- We have previously patched the kernel with the real time patch, we now want to utilize it. - The goal here is to decrease scheduler latency through changing the configs in linux.x86_64.conf: - Setting preemption model to 'Fully Preemptible Kernel (RT)' - Setting tick rate to 1000Hz. - Setting cpu governor to performance. - The above should make it possible to significantly increase the "Frame Delay" setting in RetroArch since we now have less scheduler latency and a more consistently running system - With the above changes, I am now able to set "Frame Delay" to the max value of 15 for nes, which cuts away a full frame of input latency from controller input to screen update.
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Ok thanks, I merged this for test purposes, I will build the image and we will test it together. |
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Ok I will test it when it is ready. |
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Can I ask you to upload the system and kernel file instead so I don't have to wipe my SD card with the full image? |
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Nevermind, I will just flash another SD card... |
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Hi, I tried your modified image now and using NES I can increase the Frame Delay all the way to 15 as I could with my own modified version, so looks good. I would however have liked to update Lakka to the latest unmodified nightly and verify that I now can only set Frame Delay to around 5 as I would expect, but it will not let me update. I'm getting md5/size check fails after the tar-extraction after reboot. Probably a separate issue - I think I saw you changed the partition size recently, could that be the cause? Anyway, the patch seems to work although I can't downgrade/upgrade a couple of times easily and verify the difference as I would have liked. |
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I'm not sure where this error comes from. The image I gave you already have the 512Mb partition, so have the latest unmodified nightly. Maybe the file got corrupted during download? Anyway, does the RT patch have an impact on emulation performance? |
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Yes I was able to set the frame delay to the max value of 15 which cuts away almost a full frame of delay and is not possible to do with the regular builds. Same as what I saw on my own modified rt patched builds. |
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Ok. Can you make the same patch for the i386 build please? Does this patch make sense on ARM boards where we are not using DRM/KMS? |
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Ok I will fix the i386 build as well. It should make sense for ARM boards too. |
The motivation of this pull request is to decrease controller input latency of RetroArch running on Lakka.
The pull request is split into two commits:
This cuts away a full frame of delay on my NUC setup by being able to increase the "Frame Delay" setting all the way to the max value of 15 for nes.
For now only x64 generic is configured to utilize the RT functionality of the kernel.
See commit messages for additional info:
we now want to utilize it.
changing the configs in linux.x86_64.conf:
the "Frame Delay" setting in RetroArch since we now have less
scheduler latency and a more consistently running system
to the max value of 15 for nes, which cuts away a full
frame of input latency from controller input to screen update.