On Fri, Jun 7, 2019 at 10:19 PM Martin K. Petersen <martin.petersen@xxxxxxxxxx> wrote: > > > Kashyap, > > > AMD EPYC is not efficient w.r.t QPI transaction. > [...] > > Same test on Intel architecture provides better result > > Heuristics are always hard. > > However, you are making assumptions based on observed performance of > current Intel offerings vs. current AMD offerings. This results in what > is inevitably going to be a short-lived heuristic in the kernel. Things > could easily be reversed in next generation platforms from these > vendors. > > So while I appreciate that the logic works given the machines you are > currently testing, I think CPU manufacturer is a horrible heuristic. You > are stating "This will be the right choice for all future processors > manufactured by Intel". That's a bit of a leap of faith. > > Instead of predicting the future I prefer to make decisions based on > things we know. Measured negative impact on current EPYC family, for > instance. That's a fairly well-defined and narrow scope. > > That said, I am still not a big fan of platform-specific tweaks in > drivers. While I prefer the kernel to do the right thing out of the box, > I think the module parameter is probably the better choice in this case. Martin, If we decide to remove cpu arch check later, things will be unnecessary complex to explain default driver behavior as we may have two driver behaviors. We are going to remove cpu architecture detection logic. It is good to have module parameter based dependency from day one. We will be sending relevant patch soon. Kashyap > > -- > Martin K. Petersen Oracle Linux Engineering
