CPU usage (SPEED) of > 100% is counter-intuitive, and unhelpful, IMHO

[cloudlinux]

CPU % should be relative to the total CPU of the server, not per CPU.

[ross]

Hi All,

My first post here... been converting servers to CloudLinux for the past year.

We only recently worked out that the LVE Manager setting for "CPU Usage (SPEED)" is per CPU and not for all CPUs. We (not unreasonably) assumed that 100% was the maximum processing power we could give a hosting account.

http://docs.cloudlinux.com/index.html?speed_limits.html

So in fact:

100% = 1 CPU
150% = 1.5 CPUs
300% = 3 CPUs
etc.

IMHO this is both

1. Counter-intuitive.
2. Unhelpful when it comes to the efficient per-account management of limits.

Unhelpful for this reason: if I upgrade my VPS to have more vCPU, then (if Im not mistaken), the only way I can get my hosting accounts to take better advantage of this upgrade is to edit each one of them individually to increase the "CPU Usage (SPEED) setting to a higher value.

If "CPU Usage (SPEED)" was instead relative to the whole server, then all accounts would get proportionately the same extra resources when I add CPUs to the server, without having to edit each one individually via LVE Manager. Granted, one could argue that now the reverse is true.... that if didnt want any of my existing hosting accounts to benefit from the additional server CPUs, then now Id have to edit each one individually to decrease that %. But my answer to this is:

1. The way it is now (200% = 2 CPUs) is still counter-intuitive. 100% is logically the max possible setting relative to any number of CPUs.
2. I"m going to hazard a guess (could be wrong!) and suggest that most sys admins would prefer to instantly give all accounts the benefit of a server upgrade.

If youre trying to please all the people all the time, then my best suggestion is that you give the option to make the "CPU Usage (SPEED)" an absolute setting (as it is now), OR a relative setting (as Id like it to be).

If my understanding on any of the above is incorrect, please let me know. Perhaps there IS a way to adjust settings in LVE Manager that DO make them relative to all available CPUs - is there?

Thanks for listening.

[sqh]

As far as going back to adjust your current accounts, should your hardware change, you can just edit the "DEFAULT" LVE in LVE Manager, and these settings will be applied to all existing accounts, if they are still using the Default settings. If they are not... you can click "reset" to the right of those that are not using defaults, and it will put them back on defaults (the new ones that you set)

May not help you... but thought I would share the idea, in case it is of use.

I would agree with you that it would be better to set a limit like 25% and that would give the account 25% of whatever CPU power you have.

- Scott

[iseletsk]

The CPU setting relative to the core is pretty standard across virtualization industry.

It also much more meaningful then limit related to all cores.

When someone says CPU limit of 50% --> you know exactly how much it is when it is related to single core.
You don know / cannot figure it out if it is across all the CPUs --> until you know how many CPUs are there.
It also makes it not portable -- as one of the servers might have 16 cores, and another might have 2 -> and in such case 50% would mean really different numbers.

The 3rd issue would be with precision. On 64 core servers, setting 1/2 core limit would take you into real of floating numbers, and calculating how to give 1/3 of a core on 16 core system requires people to solve mathematical equations when using CPU % relative to all cores on a server.