Add documentation for EVE memory settings. #4164
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This commit introduces a detailed documentation file that explains the memory settings for EVE OS. It covers the following topics: - Overview of cgroups and their memory limits in EVE OS. - Detailed explanation of soft and hard memory limits. - Hierarchical structure of cgroups in EVE. - Specific memory settings for EVE services and user applications. - Recommendations for adjusting memory settings. - Explanation of VMM overhead and how to override it. - Handling of Out-Of-Memory (OOM) situations. The documentation aims to provide clear guidelines for configuring memory settings to optimize the performance and stability of EVE OS. Signed-off-by: Nikolay Martyanov <nikolay@zededa.com>
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I don't see any need to wait for all of the long eden tests to run when this is just doc changes. @OhmSpectator go ahead and merge whenever you want. |
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Just FYI, #4161 makes the usage of cgroupsv1 explicit with |
Yeah, I already saw it. Actually, I want to move to v2 at some point as it provides more controls. But I have no idea what has to be changed for that. |
I think @rouming was looking at that, but I could be wrong. |
Someone may want to add more information to the document or do a test read. I've spent quite a bit of time on it, and I might have missed some obvious errors or typos because my eyes are a bit blurred and I can't see the obvious anymore. |
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Up to you. This hardly will break anything if you missed something, it is a really big step above what we have today. I would say merge it, always can open another quick small docs PR if needed. |
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Ok, let it be =D |
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Don't forget to link your doc from https://github.com/lf-edge/eve/blob/master/docs/mkdocs/mkdocs.yml |
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| Cgroups are a Linux kernel feature that limits, accounts for, and isolates the | ||
| resource usage of a collection of processes. Cgroups are used to control the | ||
| memory, CPU, and I/O resources that a process can use. |
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Should we also explain how cgroup hierarchy works since we are using it? Or maybe just add a link to some official Linux documentation?
| An indication that the EVE services require more memory can be the situation | ||
| when the EVE services are frequently hitting memory limits and the OOM killer is | ||
| fired with constraint `CONSTRAINT_NONE` and the `oom_memcg` value set to one of | ||
| the cgroups of the EVE services: |
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You probably forgot to list cgroups after the colon or the sentence should end with a fullstop.
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ooops, yep... Will create a new PR soon
| with constraint `CONSTRAINT_MEMCG` and the `oom_memcg` value set `eve` cgroup: | ||
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| ```text | ||
| oom-kill:constraint=CONSTRAINT_MEMCG,...,oom_memcg=/eve/,... |
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Maybe you already describe this somewhere, but where can the user see this oom-kill message, in dmesg and also in device logs?
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Yep, dmesg and the logs on the controller (device index). Will add it.
| #### GRUB override file | ||
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| These settings can be changed using the `set_global` command in the | ||
| GRUB override file. |
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Is this changeable after the device is onboarded?
For example, if user notices that dom0 needs more memory, is he able to change the setting remotely without re-installing the device?
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Yes, it can be set permanently by mounting the config partition and fixing the grub config.
Mount the configuration directory:
eve config mount /mnt
Add the desired kernel argument to the GRUB configuration:
echo 'set_global dom0_extra_args "<your_kernel_argument>"' >> /mnt/grub.cfg
Unmount the configuration directory:
eve config unmount
Reboot the device:
reboot
Will add it.
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@milan-zededa here are the fixes: #4169 |
This commit introduces a detailed documentation file that explains the memory settings for EVE OS. It covers the following topics:
The documentation aims to provide clear guidelines for configuring memory settings to optimize the performance and stability of EVE OS.