On 6 December 2016 at 17:42, Patrick Mooney <[email protected]>
wrote:

>
> On 6 December 2016 at 08:41, Nahum Shalman <[email protected]> wrote
>
>> Additional thoughts:
>> I wonder how bad it would be to allow the LX brand to alter how many CPUs
>> the Linux system calls see based on a zone property (probably a new one...)
>> My first instinct is "not that bad", though my second instinct is "the
>> consequences of doing so are subtle and it's probably much worse than I
>> would think".
>>
>
> This topic comes up fairly often.  It's very difficult to tell a
> convincing "lie" about how many CPUs are available on the system.  If you
> were to report only 0-7 cores out of 24, for example, software querying the
> CPU ID may still see higher identifiers if it's scheduled onto the other
> socket.  It's also possible that total CPU time enforced by the cap would
> exceed what would be theoretically possible on the virtual CPUs which have
> been presented.  (If 8.5 seconds of CPU time were consumed on those "8
> cores" in 1 second, tools like 'top' might be grumpy.)
>
> All in all, "subtle consequences" is an accurate description of why the
> task is difficult accomplish correctly.
>

I wonder if its worth looking at LXC / bhyve to see if they have any ideas
on this ?

Subtle consequences indeed !



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