Re: Kernel v4.7-rc5 - performance degradation upto 40% after disabling and re-enabling a core

[Jirka Hladky]

Hi Peter,

have you a chance to look into this? Is there anything I can do to
help you to fix it?

Thanks a lot!
Jirka


On Wed, Jun 29, 2016 at 11:58 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Wed, Jun 29, 2016 at 11:47:56AM +0200, Jirka Hladky wrote:
>> Hi Peter,
>>
>> I think Cluster on Die technology was introduced in Haswell generation. The
>> server I'm using is equipped with 4x Intel E5-4610 v2 (Ivy Bridge). I have
>> double checked the BIOS and there is no cluster on die setting.
>
> Oh right, that's E5v3..
>
>> The authors of the paper have reported the issue on AMD Bulldozer CPU which
>> also does not have COD technology.
>
> The Opteron 6272, which they use, is an Interlagos, that has something
> similar in that each package contains two nodes.
>
> And their patch touches exactly that part of the x86 topo setup, the
> match_die() && !same_node() condition, IOW same package, different node.
>
> That's not a path an Intel chip would trigger without COD support.